- 06 Jan, 2009 40 commits
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Hugh Dickins authored
Complete zap_pte_range()'s coverage of bad pagetable entries by calling print_bad_pte() on a pte_file in a linear vma and on a bad swap entry. That needs free_swap_and_cache() to tell it, which will also have shown one of those "swap_free" errors (but with much less information). Similar checks in fork's copy_one_pte()? No, that would be more noisy than helpful: we'll see them when parent and child exec or exit. Where do_nonlinear_fault() calls print_bad_pte(): omit !VM_CAN_NONLINEAR case, that could only be a bug in sys_remap_file_pages(), not a bad pte. VM_FAULT_OOM rather than VM_FAULT_SIGBUS? Well, okay, that is consistent with what happens if do_swap_page() operates a bad swap entry; but don't we have patches to be more careful about killing when VM_FAULT_OOM? Signed-off-by:
Hugh Dickins <hugh@veritas.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Rik van Riel <riel@redhat.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Hugh Dickins authored
print_bad_pte() is so far being called only when zap_pte_range() finds negative page_mapcount, or there's a fault on a pte_file where it does not belong. That's weak coverage when we suspect pagetable corruption. Originally, it was called when vm_normal_page() found an invalid pfn: but pfn_valid is expensive on some architectures and configurations, so 2.6.24 put that under CONFIG_DEBUG_VM (which doesn't help in the field), then 2.6.26 replaced it by a VM_BUG_ON (likewise). Reinstate the print_bad_pte() in vm_normal_page(), but use a cheaper test than pfn_valid(): memmap_init_zone() (used in bootup and hotplug) keep a __read_mostly note of the highest_memmap_pfn, vm_normal_page() then check pfn against that. We could call this pfn_plausible() or pfn_sane(), but I doubt we'll need it elsewhere: of course it's not reliable, but gives much stronger pagetable validation on many boxes. Also use print_bad_pte() when the pte_special bit is found outside a VM_PFNMAP or VM_MIXEDMAP area, instead of VM_BUG_ON. Signed-off-by:
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Hugh Dickins authored
Now that bad pages are kept out of circulation, there is no need for the infamous page_remove_rmap() BUG() - once that page is freed, its negative mapcount will issue a "Bad page state" message and the page won't be freed. Removing the BUG() allows more info, on subsequent pages, to be gathered. We do have more info about the page at this point than bad_page() can know - notably, what the pmd is, which might pinpoint something like low 64kB corruption - but page_remove_rmap() isn't given the address to find that. In practice, there is only one call to page_remove_rmap() which has ever reported anything, that from zap_pte_range() (usually on exit, sometimes on munmap). It has all the info, so remove page_remove_rmap()'s "Eeek" message and leave it all to zap_pte_range(). mm/memory.c already has a hardly used print_bad_pte() function, showing some of the appropriate info: extend it to show what we want for the rmap case: pte info, page info (when there is a page) and vma info to compare. zap_pte_range() already knows the pmd, but print_bad_pte() is easier to use if it works that out for itself. Some of this info is also shown in bad_page()'s "Bad page state" message. Keep them separate, but adjust them to match each other as far as possible. Say "Bad page map" in print_bad_pte(), and add a TAINT_BAD_PAGE there too. print_bad_pte() show current->comm unconditionally (though it should get repeated in the usually irrelevant stack trace): sorry, I misled Nick Piggin to make it conditional on vm_mm == current->mm, but current->mm is already NULL in the exit case. Usually current->comm is good, though exceptionally it may not be that of the mm (when "swapoff" for example). Signed-off-by:
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Hugh Dickins authored
Until now the bad_page() checkers have special-cased PageReserved, keeping those pages out of circulation thereafter. Now extend the special case to all: we want to keep ANY page with bad state out of circulation - the "free" page may well be in use by something. Leave the bad state of those pages untouched, for examination by debuggers; except for PageBuddy - leaving that set would risk bringing the page back. Signed-off-by:
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Hugh Dickins authored
Simplify the PAGE_FLAGS checking and clearing when freeing and allocating a page: check the same flags as before when freeing, clear ALL the flags (unless PageReserved) when freeing, check ALL flags off when allocating. Signed-off-by:
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Dmitri Monakhov authored
In case of error extending write may have instantiated a few blocks outside i_size. We need to trim these blocks. We have to do it *regardless* to blocksize. At least ext2, ext3 and reiserfs interpret (i_size < biggest block) condition as error. Fsck will complain about wrong i_size. Then fsck will fix the error by changing i_size according to the biggest block. This is bad because this blocks contain garbage from previous write attempt. And result in data corruption. ####TESTCASE_BEGIN $touch /mnt/test/BIG_FILE ## at this moment /mnt/test/BIG_FILE size and blocks equal to zero open("/mnt/test/BIG_FILE", O_WRONLY|O_CREAT|O_DIRECT, 0666) = 3 write(3, "aaaaaaaaaaaa"..., 104857600) = -1 ENOSPC (No space left on device) ## size and block sould't be changed because write op failed. $stat /mnt/test/BIG_FILE File: `/mnt/test/BIG_FILE' Size: 0 Blocks: 110896 IO Block: 1024 regular empty file <<<<<<<<^^^^^^^^^^^^^^^^^^^^^^^^^^^^^file size is less than biggest block idx Device: fe07h/65031d Inode: 14 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2007-01-24 20:03:38.000000000 +0300 Modify: 2007-01-24 20:03:38.000000000 +0300 Change: 2007-01-24 20:03:39.000000000 +0300 #fsck.ext3 -f /dev/VG/test e2fsck 1.39 (29-May-2006) Pass 1: Checking inodes, blocks, and sizes Inode 14, i_size is 0, should be 56556544. Fix<y>? yes Pass 2: Checking directory structure .... #####TESTCASE_ENDdiff --git a/fs/direct-io.c b/fs/direct-io.c index af0558d..4e88bea 100644 [akpm@linux-foundation.org: use i_size_read()] Signed-off-by:Dmitri Monakhov <dmonakhov@openvz.org> Cc: Zach Brown <zach.brown@oracle.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Badari Pulavarty <pbadari@us.ibm.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Dave Chinner <david@fromorbit.com> Signed-off-by:
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KOSAKI Motohiro authored
zone_is_near_oom() is unused. Signed-off-by:
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by:
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KOSAKI Motohiro authored
The vmscan bail out patch move nr_reclaimed variable to struct scan_control. Unfortunately, indirect access can easily happen cache miss. if heavy memory pressure happend, that's ok. cache miss already plenty. it is not observable. but, if memory pressure is lite, performance degression is obserbable. I compared following three pattern (it was mesured 10 times each) hackbench 125 process 3000 hackbench 130 process 3000 hackbench 135 process 3000 2.6.28-rc6 bail-out 125 130 135 125 130 135 ============================================================== 71.866 75.86 81.274 93.414 73.254 193.382 74.145 78.295 77.27 74.897 75.021 80.17 70.305 77.643 75.855 70.134 77.571 79.896 74.288 73.986 75.955 77.222 78.48 80.619 72.029 79.947 78.312 75.128 82.172 79.708 71.499 77.615 77.042 74.177 76.532 77.306 76.188 74.471 83.562 73.839 72.43 79.833 73.236 75.606 78.743 76.001 76.557 82.726 69.427 77.271 76.691 76.236 79.371 103.189 72.473 76.978 80.643 69.128 78.932 75.736 avg 72.545 76.767 78.534 76.017 77.03 93.256 std 1.89 1.71 2.41 6.29 2.79 34.16 min 69.427 73.986 75.855 69.128 72.43 75.736 max 76.188 79.947 83.562 93.414 82.172 193.382 about 4-5% degression. Then, this patch introduces a temporary local variable. result: 2.6.28-rc6 this patch num 125 130 135 125 130 135 ============================================================== 71.866 75.86 81.274 67.302 68.269 77.161 74.145 78.295 77.27 72.616 72.712 79.06 70.305 77.643 75.855 72.475 75.712 77.735 74.288 73.986 75.955 69.229 73.062 78.814 72.029 79.947 78.312 71.551 74.392 78.564 71.499 77.615 77.042 69.227 74.31 78.837 76.188 74.471 83.562 70.759 75.256 76.6 73.236 75.606 78.743 69.966 76.001 78.464 69.427 77.271 76.691 69.068 75.218 80.321 72.473 76.978 80.643 72.057 77.151 79.068 avg 72.545 76.767 78.534 70.425 74.2083 78.462 std 1.89 1.71 2.41 1.66 2.34 1.00 min 69.427 73.986 75.855 67.302 68.269 76.6 max 76.188 79.947 83.562 72.616 77.151 80.321 OK. the degression is disappeared. Signed-off-by:Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mel@csn.ul.ie> Signed-off-by:
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Rik van Riel authored
When the VM is under pressure, it can happen that several direct reclaim processes are in the pageout code simultaneously. It also happens that the reclaiming processes run into mostly referenced, mapped and dirty pages in the first round. This results in multiple direct reclaim processes having a lower pageout priority, which corresponds to a higher target of pages to scan. This in turn can result in each direct reclaim process freeing many pages. Together, they can end up freeing way too many pages. This kicks useful data out of memory (in some cases more than half of all memory is swapped out). It also impacts performance by keeping tasks stuck in the pageout code for too long. A 30% improvement in hackbench has been observed with this patch. The fix is relatively simple: in shrink_zone() we can check how many pages we have already freed, direct reclaim tasks break out of the scanning loop if they have already freed enough pages and have reached a lower priority level. We do not break out of shrink_zone() when priority == DEF_PRIORITY, to ensure that equal pressure is applied to every zone in the common case. However, in order to do this we do need to know how many pages we already freed, so move nr_reclaimed into scan_control. akpm: a historical interlude... We tried this in 2004: :commit e468e46a9bea3297011d5918663ce6d19094cf87 :Author: akpm <akpm> :Date: Thu Jun 24 15:53:52 2004 +0000 : :[PATCH] vmscan.c: dont reclaim too many pages : : The shrink_zone() logic can, under some circumstances, cause far too many : pages to be reclaimed. Say, we're scanning at high priority and suddenly hit : a large number of reclaimable pages on the LRU. : Change things so we bale out when SWAP_CLUSTER_MAX pages have been reclaimed. And we reverted it in 2006: :commit 210fe530 :Author: Andrew Morton <akpm@osdl.org> :Date: Fri Jan 6 00:11:14 2006 -0800 : : [PATCH] vmscan: balancing fix : : Revert a patch which went into 2.6.8-rc1. The changelog for that patch was: : : The shrink_zone() logic can, under some circumstances, cause far too many : pages to be reclaimed. Say, we're scanning at high priority and suddenly : hit a large number of reclaimable pages on the LRU. : : Change things so we bale out when SWAP_CLUSTER_MAX pages have been : reclaimed. : : Problem is, this change caused significant imbalance in inter-zone scan : balancing by truncating scans of larger zones. : : Suppose, for example, ZONE_HIGHMEM is 10x the size of ZONE_NORMAL. The zone : balancing algorithm would require that if we're scanning 100 pages of : ZONE_HIGHMEM, we should scan 10 pages of ZONE_NORMAL. But this logic will : cause the scanning of ZONE_HIGHMEM to bale out after only 32 pages are : reclaimed. Thus effectively causing smaller zones to be scanned relatively : harder than large ones. : : Now I need to remember what the workload was which caused me to write this : patch originally, then fix it up in a different way... And we haven't demonstrated that whatever problem caused that reversion is not being reintroduced by this change in 2008. Signed-off-by:
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Hannes Eder authored
Fix the following sparse warnings: mm/hugetlb.c:375:3: warning: returning void-valued expression mm/hugetlb.c:408:3: warning: returning void-valued expression Signed-off-by:
Hannes Eder <hannes@hanneseder.net> Acked-by:
Nishanth Aravamudan <nacc@us.ibm.com> Signed-off-by:
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Hugh Dickins authored
Remove the srandom32((u32)get_seconds()) from non-rotational swapon: there's been a coincidental discussion of earlier randomization, assume that goes ahead, let swapon be a client rather than stirring for itself. Signed-off-by:
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Hugh Dickins authored
Change pgoff_t nr_blocks in discard_swap() and discard_swap_cluster() to sector_t: given the constraints on swap offsets (in particular, the 5 bits of swap type accommodated in the same unsigned long), pgoff_t was actually safe as is, but it certainly looked worrying when shifted left. [akpm@linux-foundation.org: fix shift overflow] Signed-off-by:
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Hugh Dickins authored
Though attempting to find free clusters (Andrea), swap allocation has always restarted its searches from the beginning of the swap area (sct), to reduce seek times between swap pages, by not scattering them all over the partition. But on a solidstate swap device, seeks are cheap, and block remapping to level the wear may be limited by zones: in that case it's better to cycle around the whole partition. Signed-off-by:
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Hugh Dickins authored
Swap allocation has always started from the beginning of the swap area; but if we're dealing with a solidstate swap device which can only remap blocks within limited zones, that would sooner wear out the first zone. Therefore sys_swapon() test whether blk_queue is non-rotational, and if so randomize the cluster_next starting position for allocation. If blk_queue is nonrot, note SWP_SOLIDSTATE for later use, and report it with an "SS" at the right end of the kernel's "Adding ... swap" message (so that if it's both nonrot and discardable, "SSD" will be shown there). Perhaps something should be shown in /proc/swaps (swapon -s), but we have to be more cautious before making any addition to that format. Signed-off-by:
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Hugh Dickins authored
When scan_swap_map() finds a free cluster of swap pages to allocate, discard the old contents of the cluster if the device supports discard. But don't bother when swap is so fragmented that we allocate single pages. Be careful about racing allocations made while we're scanning for a cluster; and hold up allocations made while we're discarding. Signed-off-by:
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Hugh Dickins authored
When adding swap, all the old data on swap can be forgotten: sys_swapon() discard all but the header page of the swap partition (or every extent but the header of the swap file), to give a solidstate swap device the opportunity to optimize its wear-levelling. If that succeeds, note SWP_DISCARDABLE for later use, and report it with a "D" at the right end of the kernel's "Adding ... swap" message. Perhaps something should be shown in /proc/swaps (swapon -s), but we have to be more cautious before making any addition to that format. Signed-off-by:
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Hugh Dickins authored
Before making functional changes, rearrange scan_swap_map() to simplify subsequent diffs. Actually, there is one functional change in there: leave cluster_nr negative while scanning for a new cluster - resetting it early increased the likelihood that when we have difficulty finding a free cluster, another task may come in and try doing exactly the same - just a waste of cpu. Before making functional changes, rearrange struct swap_info_struct slightly: flags will be needed as an unsigned long (for wait_on_bit), next is a good int to pair with prio, old_block_size is uninteresting so shift it to the end. Signed-off-by:
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Hugh Dickins authored
The kernel has not supported v0 SWAP-SPACE since 2.5.22: I think we can now safely drop its "version 0 swap is no longer supported" message - just say "Unable to find swap-space signature" as usual. This removes one level of indentation from a stretch of sys_swapon(). I'd have liked to be specific, saying "Unable to find SWAPSPACE2 signature", but it's just too confusing that the version 1 signature shows the number 2. Irrelevant nearby cleanup: kmap(page) already gives page_address(page). Signed-off-by:
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Hugh Dickins authored
Remove trailing whitespace from swapfile.c, and odd swap_show() alignment. Signed-off-by:
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Hugh Dickins authored
Remove the SWP_ACTIVE mask: it just obscures the SWP_WRITEOK flag. Signed-off-by:
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Hugh Dickins authored
sys_swapon()'s swapfilesize (better renamed swapfilepages) is declared as an int, but should be an unsigned long like the maxpages it's compared against: on 64-bit (with 4kB pages) a swapfile of 2^44 bytes was rejected with "Swap area shorter than signature indicates". Signed-off-by:
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KOSAKI Motohiro authored
Sparse output following warnings. mm/vmalloc.c:1436:6: warning: symbol 'vread' was not declared. Should it be static? mm/vmalloc.c:1474:6: warning: symbol 'vwrite' was not declared. Should it be static? However, it is used by /dev/kmem. fixed here. Signed-off-by:
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KOSAKI Motohiro authored
Sparse output following warning. mm/page_alloc.c:4301:6: warning: symbol 'setup_per_zone_inactive_ratio' was not declared. Should it be static? cleanup here. Signed-off-by:
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KOSAKI Motohiro authored
sparse output following warning mm/vmscan.c:2507:6: warning: symbol 'scan_zone_unevictable_pages' was not declared. Should it be static? cleanup here. Signed-off-by:
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KOSAKI Motohiro authored
sparse output following warning. mm/vmscan.c:2549:6: warning: symbol 'scan_all_zones_unevictable_pages' was not declared. Should it be static? cleanup here. Signed-off-by:
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KOSAKI Motohiro authored
Sparse output following warnings. mm/memcontrol.c:782:5: warning: symbol 'mem_cgroup_resize_limit' was not declared. Should it be static? cleanup here. Signed-off-by:
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KOSAKI Motohiro authored
sparse output following warnings. mm/memory.c:2936:8: warning: incorrect type in assignment (different address spaces) mm/memory.c:2936:8: expected void *maddr mm/memory.c:2936:8: got void [noderef] <asn:2> cleanup here. Signed-off-by:
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KOSAKI Motohiro authored
Sparse output following warning. mm/page_cgroup.c:100:15: warning: symbol 'init_section_page_cgroup' was not declared. Should it be static? cleanup here. Signed-off-by:
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KOSAKI Motohiro authored
memcg reclaim shouldn't change zone->recent_rotated statistics. If memcgroup reclaim changes zone statistics, global reclaim can get a bit confused. Signed-off-by:
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Hugh Dickins authored
Rik suggests a simplified get_scan_ratio() for !CONFIG_SWAP. Yes, the gcc optimizer gives us that, when nr_swap_pages is #defined as 0L. Move usual declaration to swapfile.c: it never belonged in page_alloc.c. Signed-off-by:
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Hugh Dickins authored
If we add a failing stub for add_to_swap(), then we can remove the #ifdef CONFIG_SWAP from mm/vmscan.c. This was intended as a source cleanup, but looking more closely, it turns out that the !CONFIG_SWAP case was going to keep_locked for an anonymous page, whereas now it goes to the more suitable activate_locked, like the CONFIG_SWAP nr_swap_pages 0 case. Signed-off-by:
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Hugh Dickins authored
Remove gfp_mask argument from add_to_swap(): it's misleading because its only caller, shrink_page_list(), is not atomic at that point; and in due course (implementing discard) we'll sometimes want to allocate some memory with GFP_NOIO (as is used in swap_writepage) when allocating swap. No change to the gfp_mask passed down to add_to_swap_cache(): still use __GFP_HIGH without __GFP_WAIT (with nomemalloc and nowarn as before): though it's not obvious if that's the best combination to ask for here. Signed-off-by:
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Hugh Dickins authored
An unfortunate feature of the Unevictable LRU work was that reclaiming an anonymous page involved an extra scan through the anon_vma: to check that the page is evictable before allocating swap, because the swap could not be freed reliably soon afterwards. Now try_to_free_swap() has replaced remove_exclusive_swap_page(), that's not an issue any more: remove try_to_munlock() call from shrink_page_list(), leaving it to try_to_munmap() to discover if the page is one to be culled to the unevictable list - in which case then try_to_free_swap(). Update unevictable-lru.txt to remove comments on the try_to_munlock() in shrink_page_list(), and shorten some lines over 80 columns. Signed-off-by:
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Hugh Dickins authored
There's a possible race in try_to_unuse() which Nick Piggin led me to two years ago. Where it does lock_page() after read_swap_cache_async(), what if another task removed that page from swapcache just before we locked it? It would sail though the (*swap_map > 1) tests doing nothing (because it could not have been removed from swapcache before its swap references were gone), until it reaches the delete_from_swap_cache(page) near the bottom. Now imagine that this page has been allocated to swap on a different swap area while we dropped page lock (perhaps at the top, perhaps in unuse_mm): we could wrongly remove from swap cache before the page has been written to swap, so a subsequent do_swap_page() would read in stale data from swap. I think this case could not happen before: remove_exclusive_swap_page() refused while page count was raised. But now with reuse_swap_page() and try_to_free_swap() removing from swap cache without minding page count, I think it could happen - the previous patch argued that it was safe because try_to_unuse() already ignored page count, but overlooked that it might be breaking the assumptions in try_to_unuse() itself. Signed-off-by:
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Hugh Dickins authored
remove_exclusive_swap_page(): its problem is in living up to its name. It doesn't matter if someone else has a reference to the page (raised page_count); it doesn't matter if the page is mapped into userspace (raised page_mapcount - though that hints it may be worth keeping the swap): all that matters is that there be no more references to the swap (and no writeback in progress). swapoff (try_to_unuse) has been removing pages from swapcache for years, with no concern for page count or page mapcount, and we used to have a comment in lookup_swap_cache() recognizing that: if you go for a page of swapcache, you'll get the right page, but it could have been removed from swapcache by the time you get page lock. So, give up asking for exclusivity: get rid of remove_exclusive_swap_page(), and remove_exclusive_swap_page_ref() and remove_exclusive_swap_page_count() which were spawned for the recent LRU work: replace them by the simpler try_to_free_swap() which just checks page_swapcount(). Similarly, remove the page_count limitation from free_swap_and_count(), but assume that it's worth holding on to the swap if page is mapped and swap nowhere near full. Add a vm_swap_full() test in free_swap_cache()? It would be consistent, but I think we probably have enough for now. Signed-off-by:
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Hugh Dickins authored
A good place to free up old swap is where do_wp_page(), or do_swap_page(), is about to redirty the page: the data on disk is then stale and won't be read again; and if we do decide to write the page out later, using the previous swap location makes an unnecessary disk seek very likely. So give can_share_swap_page() the side-effect of delete_from_swap_cache() when it safely can. And can_share_swap_page() was always a misleading name, the more so if it has a side-effect: rename it reuse_swap_page(). Irrelevant cleanup nearby: remove swap_token_default_timeout definition from swap.h: it's used nowhere. Signed-off-by:
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Hugh Dickins authored
An application may rely on get_user_pages() to give it pages writable from userspace and shared with a driver, GUP breaking COW if necessary. It may mprotect() the pages' writability, off and on, from time to time. Normally this works fine (so long as the app does not fork); but just occasionally, under memory pressure, a readonly pte in a newly writable area is COWed unnecessarily, breaking the link with the driver: because do_wp_page() does trylock_page, and falls back to COW whenever that fails. For reliable behaviour in the unshared case, when the trylock_page fails, now unlock pagetable, lock page and relock pagetable, before deciding whether Copy-On-Write is really necessary. Reported-by: Zhou Yingchao Signed-off-by:
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Hugh Dickins authored
do_wp_page()'s VM_FAULT_WRITE return value tells __get_user_pages() that COW has been done if necessary, though it may be leaving the pte without write permission - for the odd case of forced writing to a readonly vma for ptrace. At present GUP then retries the follow_page() without asking for write permission, to escape an endless loop when forced. But an application may be relying on GUP to guarantee a writable page which won't be COWed again when written from userspace, whereas a race here might leave a readonly pte in place? Change the VM_FAULT_WRITE handling to ask follow_page() for write permission again, except in that odd case of forced writing to a readonly vma. Signed-off-by:
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David Rientjes authored
This change introduces two new sysctls to /proc/sys/vm: dirty_background_bytes and dirty_bytes. dirty_background_bytes is the counterpart to dirty_background_ratio and dirty_bytes is the counterpart to dirty_ratio. With growing memory capacities of individual machines, it's no longer sufficient to specify dirty thresholds as a percentage of the amount of dirtyable memory over the entire system. dirty_background_bytes and dirty_bytes specify quantities of memory, in bytes, that represent the dirty limits for the entire system. If either of these values is set, its value represents the amount of dirty memory that is needed to commence either background or direct writeback. When a `bytes' or `ratio' file is written, its counterpart becomes a function of the written value. For example, if dirty_bytes is written to be 8096, 8K of memory is required to commence direct writeback. dirty_ratio is then functionally equivalent to 8K / the amount of dirtyable memory: dirtyable_memory = free pages + mapped pages + file cache dirty_background_bytes = dirty_background_ratio * dirtyable_memory -or- dirty_background_ratio = dirty_background_bytes / dirtyable_memory AND dirty_bytes = dirty_ratio * dirtyable_memory -or- dirty_ratio = dirty_bytes / dirtyable_memory Only one of dirty_background_bytes and dirty_background_ratio may be specified at a time, and only one of dirty_bytes and dirty_ratio may be specified. When one sysctl is written, the other appears as 0 when read. The `bytes' files operate on a page size granularity since dirty limits are compared with ZVC values, which are in page units. Prior to this change, the minimum dirty_ratio was 5 as implemented by get_dirty_limits() although /proc/sys/vm/dirty_ratio would show any user written value between 0 and 100. This restriction is maintained, but dirty_bytes has a lower limit of only one page. Also prior to this change, the dirty_background_ratio could not equal or exceed dirty_ratio. This restriction is maintained in addition to restricting dirty_background_bytes. If either background threshold equals or exceeds that of the dirty threshold, it is implicitly set to half the dirty threshold. Acked-by:
Peter Zijlstra <peterz@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Christoph Lameter <cl@linux-foundation.org> Signed-off-by:
David Rientjes <rientjes@google.com> Cc: Andrea Righi <righi.andrea@gmail.com> Signed-off-by:
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David Rientjes authored
The background dirty and dirty limits are better defined with type specifiers of unsigned long since negative writeback thresholds are not possible. These values, as returned by get_dirty_limits(), are normally compared with ZVC values to determine whether writeback shall commence or be throttled. Such page counts cannot be negative, so declaring the page limits as signed is unnecessary. Acked-by:
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