linux-kernel - Re: [PATCH v7 0/6] vfs: Use dlock list for SB's s

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Date:   Fri, 27 Oct 2017 08:58:34 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     Waiman Long <longman@...hat.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.com>,
        Jeff Layton <jlayton@...chiereds.net>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andi Kleen <andi@...stfloor.org>,
        Dave Chinner <dchinner@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>
Subject: Re: [PATCH v7 0/6] vfs: Use dlock list for SB's s_inodes list

On Thu, Oct 26, 2017 at 02:28:55PM -0400, Waiman Long wrote:
> On 10/05/2017 02:43 PM, Waiman Long wrote:
> >
> > This is a follow up of the following patchset:
> >
> >   [PATCH v7 0/4] vfs: Use per-cpu list for SB's s_inodes list
> >   https://lkml.org/lkml/2016/4/12/1009
> >
> > This patchset provides new APIs for a set of distributed locked lists
> > (one/CPU core) to minimize lock and cacheline contention. Insertion
> > and deletion to the list will be cheap and relatively contention free.
> > Lookup, on the other hand, may be a bit more costly as there are
> > multiple lists to iterate. This is not really a problem for the
> > replacement of superblock's inode list by dlock list included in
> > the patchset as lookup isn't needed.
> >
> > For use cases that need to do lookup, the dlock list can also be
> > treated as a set of hashed lists that scales with the number of CPU
> > cores in the system.
> >
> > Both patches 5 and 6 are added to support other use cases like epoll
> > nested callbacks, for example, which could use the dlock-list to
> > reduce lock contention problem.
> >
> > Patch 1 introduces the dlock list. The list heads are allocated
> > by kcalloc() instead of percpu_alloc(). Each list head entry is
> > cacheline aligned to minimize contention.
> >
> > Patch 2 replaces the use of list_for_each_entry_safe() in
> > evict_inodes() and invalidate_inodes() by list_for_each_entry().
> >
> > Patch 3 modifies the superblock and inode structures to use the dlock
> > list. The corresponding functions that reference those structures
> > are modified.
> >
> > Patch 4 makes the sibling CPUs use the same dlock list head to reduce
> > the number of list heads that need to be iterated.
> >
> > Patch 5 enables alternative use case of as a set of hashed lists.
> >
> > Patch 6 provides an irq safe mode specified at dlock-list allocation
> > time so that it can be within interrupt context.
> >
> > Jan Kara (1):
> >   vfs: Remove unnecessary list_for_each_entry_safe() variants
> >
> > Waiman Long (5):
> >   lib/dlock-list: Distributed and lock-protected lists
> >   vfs: Use dlock list for superblock's inode list
> >   lib/dlock-list: Make sibling CPUs share the same linked list
> >   lib/dlock-list: Enable faster lookup with hashing
> >   lib/dlock-list: Add an IRQ-safe mode to be used in interrupt handler
> >
> >  fs/block_dev.c             |   9 +-
> >  fs/drop_caches.c           |   9 +-
> >  fs/inode.c                 |  38 +++---
> >  fs/notify/fsnotify.c       |   9 +-
> >  fs/quota/dquot.c           |  14 +-
> >  fs/super.c                 |   7 +-
> >  include/linux/dlock-list.h | 245 ++++++++++++++++++++++++++++++++++
> >  include/linux/fs.h         |   8 +-
> >  lib/Makefile               |   2 +-
> >  lib/dlock-list.c           | 322 +++++++++++++++++++++++++++++++++++++++++++++
> >  10 files changed, 609 insertions(+), 54 deletions(-)
> >  create mode 100644 include/linux/dlock-list.h
> >  create mode 100644 lib/dlock-list.c
> >
> Is there other objections about merging this patch series? With the
> additional patches 8 & 9 that I sent out on Oct 17, I think I had
> addressed all the concerns that I received so far. Please let me know
> what else do I need to do to make these patches mergeable?
> 

Hi Waiman,

Have you read my email about the dlist_for_each_entry_safe():

	https://marc.info/?l=linux-kernel&m=150831690725964&w=2

?

Regards,
Boqun

> Thanks,
> Longman
> 
> 

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