From: Jan Kara <jack@suse.cz> To: Andrew Morton <akpm@linux-foundation.org> Cc: Jan Kara <jack@suse.cz>, LKML <linux-kernel@vger.kernel.org>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 2/6] fs: Take mapping lock in generic read paths Date: Mon, 4 Feb 2013 13:47:15 +0100 [thread overview] Message-ID: <20130204124715.GF7523@quack.suse.cz> (raw) In-Reply-To: <20130131155940.7b1f8e0e.akpm@linux-foundation.org> On Thu 31-01-13 15:59:40, Andrew Morton wrote: > On Thu, 31 Jan 2013 22:49:50 +0100 > Jan Kara <jack@suse.cz> wrote: > > > Add mapping lock to struct address_space and grab it in all paths > > creating pages in page cache to read data into them. That means buffered > > read, readahead, and page fault code. > > Boy, this does look expensive in both speed and space. I'm not sure I'll be able to do much with the space cost but hopefully the CPU cost could be reduced. > As you pointed out in [0/n], it's 2-3%. As always with pagecache > stuff, the cost of filling the page generally swamps any inefficiencies > in preparing that page. Yes, I measured it with with ramdisk backed fs exactly to remove the cost of filling the page from the picture. But there are systems where IO is CPU bound (e.g. when you have PCIe attached devices) and although there is the additional cost of block layer which will further hide the cost of page cache itself I assume the added 2-3% incurred by page cache itself will be measurable on such systems. So that's why I'd like to reduce the CPU cost of range locking. Honza -- Jan Kara <jack@suse.cz> SUSE Labs, CR
WARNING: multiple messages have this Message-ID (diff)
From: Jan Kara <jack@suse.cz> To: Andrew Morton <akpm@linux-foundation.org> Cc: Jan Kara <jack@suse.cz>, LKML <linux-kernel@vger.kernel.org>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 2/6] fs: Take mapping lock in generic read paths Date: Mon, 4 Feb 2013 13:47:15 +0100 [thread overview] Message-ID: <20130204124715.GF7523@quack.suse.cz> (raw) In-Reply-To: <20130131155940.7b1f8e0e.akpm@linux-foundation.org> On Thu 31-01-13 15:59:40, Andrew Morton wrote: > On Thu, 31 Jan 2013 22:49:50 +0100 > Jan Kara <jack@suse.cz> wrote: > > > Add mapping lock to struct address_space and grab it in all paths > > creating pages in page cache to read data into them. That means buffered > > read, readahead, and page fault code. > > Boy, this does look expensive in both speed and space. I'm not sure I'll be able to do much with the space cost but hopefully the CPU cost could be reduced. > As you pointed out in [0/n], it's 2-3%. As always with pagecache > stuff, the cost of filling the page generally swamps any inefficiencies > in preparing that page. Yes, I measured it with with ramdisk backed fs exactly to remove the cost of filling the page from the picture. But there are systems where IO is CPU bound (e.g. when you have PCIe attached devices) and although there is the additional cost of block layer which will further hide the cost of page cache itself I assume the added 2-3% incurred by page cache itself will be measurable on such systems. So that's why I'd like to reduce the CPU cost of range locking. Honza -- Jan Kara <jack@suse.cz> SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2013-02-04 12:47 UTC|newest] Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-01-31 21:49 [PATCH 0/6 RFC] Mapping range lock Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 21:49 ` [PATCH 1/6] lib: Implement range locks Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 23:57 ` Andrew Morton 2013-01-31 23:57 ` Andrew Morton 2013-02-04 16:41 ` Jan Kara 2013-02-04 16:41 ` Jan Kara 2013-02-11 5:42 ` Michel Lespinasse 2013-02-11 5:42 ` Michel Lespinasse 2013-02-11 10:27 ` Jan Kara 2013-02-11 10:27 ` Jan Kara 2013-02-11 11:03 ` Michel Lespinasse 2013-02-11 11:03 ` Michel Lespinasse 2013-02-11 12:58 ` Jan Kara 2013-02-11 12:58 ` Jan Kara 2013-01-31 21:49 ` [PATCH 2/6] fs: Take mapping lock in generic read paths Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 23:59 ` Andrew Morton 2013-01-31 23:59 ` Andrew Morton 2013-02-04 12:47 ` Jan Kara [this message] 2013-02-04 12:47 ` Jan Kara 2013-02-08 14:59 ` Jan Kara 2013-02-08 14:59 ` Jan Kara 2013-01-31 21:49 ` [PATCH 3/6] fs: Provide function to take mapping lock in buffered write path Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 21:49 ` [PATCH 4/6] fs: Don't call dio_cleanup() before submitting all bios Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 21:49 ` [PATCH 5/6] fs: Take mapping lock during direct IO Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 21:49 ` [PATCH 6/6] ext3: Convert ext3 to use mapping lock Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-02-01 0:07 ` [PATCH 0/6 RFC] Mapping range lock Andrew Morton 2013-02-01 0:07 ` Andrew Morton 2013-02-04 9:29 ` Zheng Liu 2013-02-04 9:29 ` Zheng Liu 2013-02-04 12:38 ` Jan Kara 2013-02-04 12:38 ` Jan Kara 2013-02-05 23:25 ` Dave Chinner 2013-02-05 23:25 ` Dave Chinner 2013-02-06 19:25 ` Jan Kara 2013-02-06 19:25 ` Jan Kara 2013-02-07 2:43 ` Dave Chinner 2013-02-07 2:43 ` Dave Chinner 2013-02-07 11:06 ` Jan Kara 2013-02-07 11:06 ` Jan Kara
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20130204124715.GF7523@quack.suse.cz \ --to=jack@suse.cz \ --cc=akpm@linux-foundation.org \ --cc=linux-fsdevel@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mm@kvack.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.