From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([222.73.24.84]:16501 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1755022Ab2GKBrD (ORCPT ); Tue, 10 Jul 2012 21:47:03 -0400 Message-ID: <4FFCDDA3.4000002@cn.fujitsu.com> Date: Wed, 11 Jul 2012 09:57:55 +0800 From: Liu Bo MIME-Version: 1.0 To: Josef Bacik CC: "linux-btrfs@vger.kernel.org" Subject: Re: [PATCH RFC] Btrfs: improve multi-thread buffer read References: <1341919679-13792-1-git-send-email-liubo2009@cn.fujitsu.com> <20120710185822.GE7529@localhost.localdomain> In-Reply-To: <20120710185822.GE7529@localhost.localdomain> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 07/11/2012 02:58 AM, Josef Bacik wrote: > On Tue, Jul 10, 2012 at 05:27:59AM -0600, Liu Bo wrote: >> While testing with my buffer read fio jobs[1], I find that btrfs does not >> perform well enough. >> >> Here is a scenario in fio jobs: >> >> We have 4 threads, "t1 t2 t3 t4", starting to buffer read a same file, >> and all of them will race on add_to_page_cache_lru(), and if one thread >> successfully puts its page into the page cache, it takes the responsibility >> to read the page's data. >> >> And what's more, reading a page needs a period of time to finish, in which >> other threads can slide in and process rest pages: >> >> t1 t2 t3 t4 >> add Page1 >> read Page1 add Page2 >> | read Page2 add Page3 >> | | read Page3 add Page4 >> | | | read Page4 >> -----|------------|-----------|-----------|-------- >> v v v v >> bio bio bio bio >> >> Now we have four bios, each of which holds only one page since we need to >> maintain consecutive pages in bio. Thus, we can end up with far more bios >> than we need. >> >> Here we're going to >> a) delay the real read-page section and >> b) try to put more pages into page cache. >> >> With that said, we can make each bio hold more pages and reduce the number >> of bios we need. >> >> Here is some numbers taken from fio results: >> w/o patch w patch >> ------------- -------- --------------- >> READ: 745MB/s +32% 987MB/s >> > > Um, I have this in btrfs-next > > Btrfs: use large extent range for read and its endio > > that seems to do the same thing, did you not want to do that anymore? Thanks, > I'm still hard working on that patchset. :) Although the patchset is well worthy of testing, it is not good enough for btrfs upstream. While doing some tuning work on it, I realized that I could make this improvement without the help of rwlock extent state stuff, so I made this smaller and cleaner patch for upstream so that we could gain some performance here first. thanks, liubo > Josef > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >