linux-kernel - Re: [PATCH 8/8] vm: Add an tuning knob for vm.max_writeback

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1253806696.18939.40.camel@laptop>
Date:	Thu, 24 Sep 2009 17:38:16 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Jan Kara <jack@...e.cz>, Chris Mason <chris.mason@...cle.com>,
	Artem Bityutskiy <dedekind1@...il.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"david@...morbit.com" <david@...morbit.com>,
	"hch@...radead.org" <hch@...radead.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH 8/8] vm: Add an tuning knob for vm.max_writeback_mb

On Thu, 2009-09-24 at 16:33 +0800, Wu Fengguang wrote:

> Yeah, FIFO queuing should be good enough.
> 
> I'd like to propose one more data structure for evaluation :)
> 
> - bdi->throttle_lock
> - bdi->throttle_list    pages to sync for each waiting task, taken from sync_writeback_pages()
> - bdi->throttle_pages   (counted down) pages to sync for the head task, shall be atomic_t
> 
> In balance_dirty_pages(), it would do
> 
>         nr_to_sync = sync_writeback_pages()
>         if (list_empty(bdi->throttle_list))  # I'm the only task
>                 bdi->throttle_pages = nr_to_sync
>         append nr_to_sync to bdi->throttle_list
>         kick off background writeback
>         wait
>         remove itself from bdi->throttle_list and wait list
>         set bdi->throttle_pages for new head task (or LONG_MAX)
> 
> In __bdi_writeout_inc(), it would do
> 
>         if (--bdi->throttle_pages <= 0)
>                 check and wake up head task
> 
> In wb_writeback(), it would do
> 
>         if (args->for_background && exiting)
>                 wake up all throttled tasks
> 
> To prevent wake up too many tasks at the same time, it can relax the
> background threshold a bit, so that __bdi_writeout_inc() become the
> only wake up point in normal cases.
> 
>         if (args->for_background && !list_empty(bdi->throttle_list) &&
>                 over background_thresh - background_thresh / 32)
>                 keep write pages;

Right, something like that ought to work well, or at least sounds like
worth a try ;-)

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/