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  1. 31 May, 2018 6 commits
    • Paolo Valente's avatar
      block, bfq: remove slow-system class · e24f1c24
      Paolo Valente authored 
      BFQ computes the duration of weight raising for interactive
applications automatically, using some reference parameters. In
particular, BFQ uses the best durations (see comments in the code for
how these durations have been assessed) for two classes of systems:
slow and fast ones. Examples of slow systems are old phones or systems
using micro HDDs. Fast systems are all the remaining ones. Using these
parameters, BFQ computes the actual duration of the weight raising,
for the system at hand, as a function of the relative speed of the
system w.r.t. the speed of a reference system, belonging to the same
class of systems as the system at hand.

This slow vs fast differentiation proved to be useful in the past, but
happens to have little meaning with current hardware. Even worse, it
does cause problems in virtual systems, where the speed of the system
can vary frequently, and so widely to just confuse the class-detection
mechanism, and, as we have verified experimentally, to cause BFQ to
compute non-sensical weight-raising durations.

This commit addresses this issue by removing the slow class and the
class-detection mechanism.
Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      e24f1c24
    • Paolo Valente's avatar
      block, bfq: add description of weight-raising heuristics · 4029eef1
      Paolo Valente authored 
      A description of how weight raising works is missing in BFQ
sources. In addition, the code for handling weight raising is
scattered across a few functions. This makes it rather hard to
understand the mechanism and its rationale. This commits adds such a
description at the beginning of the main source file.
Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      4029eef1
    • Filippo Muzzini's avatar
      block, bfq: remove the removal of 'next' rq in bfq_requests_merged · ac857e0d
      Filippo Muzzini authored 
      Since bfq_finish_request() is always called on the request 'next',
after bfq_requests_merged() is finished, and bfq_finish_request()
removes 'next' from its bfq_queue if needed, it isn't necessary to do
such a removal in advance in bfq_merged_requests().

This commit removes such a useless 'next' removal.
Signed-off-by: default avatarFilippo Muzzini <filippo.muzzini@outlook.it>
Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      ac857e0d
    • Paolo Valente's avatar
      block, bfq: remove wrong check in bfq_requests_merged · 8abfa4d6
      Paolo Valente authored 
      The request rq passed to the function bfq_requests_merged is always in
a bfq_queue, so the check !RB_EMPTY_NODE(&rq->rb_node) at the
beginning of bfq_requests_merged always succeeds, and the control
flow systematically skips to the end of the function.  This implies
that the body of the function is never executed, i.e., the
repositioning of rq is never performed.

On the opposite end, a control is missing in the body of the function:
'next' must be removed only if it is inside a bfq_queue.

This commit removes the wrong check on rq, and adds the missing check
on 'next'. In addition, this commit adds comments on
bfq_requests_merged.
Signed-off-by: default avatarFilippo Muzzini <filippo.muzzini@outlook.it>
Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      8abfa4d6
    • Filippo Muzzini's avatar
      block, bfq: remove wrong lock in bfq_requests_merged · a12bffeb
      Filippo Muzzini authored 
      In bfq_requests_merged(), there is a deadlock because the lock on
bfqq->bfqd->lock is held by the calling function, but the code of
this function tries to grab the lock again.

This deadlock is currently hidden by another bug (fixed by next commit
for this source file), which causes the body of bfq_requests_merged()
to be never executed.

This commit removes the deadlock by removing the lock/unlock pair.
Signed-off-by: default avatarFilippo Muzzini <filippo.muzzini@outlook.it>
Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      a12bffeb
    • Jens Axboe's avatar
      block: fixup bioset_integrity_create() call · 04c4950d
      Jens Axboe authored 
      Missed converting the bioset_integrity_create() bounce bio set
call.

Fixes: 338aa96d ("block: convert bounce, q->bio_split to bioset_init()/mempool_init()")
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      04c4950d
  3. 30 May, 2018 18 commits
  5. 29 May, 2018 16 commits
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