From: Dave Hansen <firstname.lastname@example.org> To: Jan Kara <email@example.com>, Andi Kleen <firstname.lastname@example.org> Cc: email@example.com, Mel Gorman <firstname.lastname@example.org>, "Kirill A. Shutemov" <email@example.com>, firstname.lastname@example.org Subject: Re: [PATCH 0/7 v1] Speed up page cache truncation Date: Wed, 11 Oct 2017 10:34:47 -0700 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <20171011080658.GK3667@quack2.suse.cz> On 10/11/2017 01:06 AM, Jan Kara wrote: >>> when rebasing our enterprise distro to a newer kernel (from 4.4 to 4.12) we >>> have noticed a regression in bonnie++ benchmark when deleting files. >>> Eventually we have tracked this down to a fact that page cache truncation got >>> slower by about 10%. There were both gains and losses in the above interval of >>> kernels but we have been able to identify that commit 83929372f629 "filemap: >>> prepare find and delete operations for huge pages" caused about 10% regression >>> on its own. >> It's odd that just checking if some pages are huge should be that >> expensive, but ok .. > Yeah, I was surprised as well but profiles were pretty clear on this - part > of the slowdown was caused by loads of page->_compound_head (PageTail() > and page_compound() use that) which we previously didn't have to load at > all, part was in hpage_nr_pages() function and its use. Well, page->_compound_head is part of the same cacheline as the rest of the page, and the page is surely getting touched during truncation at _some_ point. The hpage_nr_pages() might cause the cacheline to get loaded earlier than before, but I can't imagine that it's that expensive. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to firstname.lastname@example.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"email@example.com"> firstname.lastname@example.org </a>
next prev parent reply other threads:[~2017-10-11 17:34 UTC|newest] Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-10-10 15:19 Jan Kara 2017-10-10 15:19 ` Jan Kara 2017-10-10 15:19 ` [PATCH 1/7] mm: Speedup cancel_dirty_page() for clean pages Jan Kara 2017-10-10 15:19 ` Jan Kara 2017-10-10 15:19 ` [PATCH 2/7] mm: Refactor truncate_complete_page() Jan Kara 2017-10-10 15:19 ` Jan Kara 2017-10-10 15:19 ` [PATCH 3/7] mm: Factor out page cache page freeing into a separate function Jan Kara 2017-10-10 15:19 ` Jan Kara 2017-10-10 15:19 ` [PATCH 4/7] mm: Move accounting updates before page_cache_tree_delete() Jan Kara 2017-10-10 15:19 ` Jan Kara 2017-10-10 15:19 ` [PATCH 5/7] mm: Move clearing of page->mapping to page_cache_tree_delete() Jan Kara 2017-10-10 15:19 ` Jan Kara 2017-10-10 15:19 ` [PATCH 6/7] mm: Factor out checks and accounting from __delete_from_page_cache() Jan Kara 2017-10-10 15:19 ` Jan Kara 2017-10-10 15:19 ` [PATCH 7/7] mm: Batch radix tree operations when truncating pages Jan Kara 2017-10-10 15:19 ` Jan Kara 2017-10-11 7:39 ` Mel Gorman 2017-10-17 23:05 ` Andrew Morton 2017-10-17 23:05 ` Andrew Morton 2017-10-18 10:44 ` Jan Kara 2017-10-10 17:25 ` [PATCH 0/7 v1] Speed up page cache truncation Andi Kleen 2017-10-10 17:25 ` Andi Kleen 2017-10-11 8:06 ` Jan Kara 2017-10-11 16:51 ` Andi Kleen 2017-10-11 17:34 ` Dave Hansen [this message] 2017-10-11 17:59 ` Mel Gorman 2017-10-11 18:37 ` Andi Kleen 2017-10-11 21:06 ` Jan Kara 2017-10-11 21:24 ` Dave Chinner 2017-10-12 9:09 ` Mel Gorman 2017-10-12 14:07 ` Jan Kara
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