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Date: Tue, 12 Jan 2021 09:35:34 -0800 From: Linus Torvalds <torvalds@...ux-foundation.org> To: Jan Kara <jack@...e.cz> Cc: Hugh Dickins <hughd@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, Matthew Wilcox <willy@...radead.org>, syzbot <syzbot+2fc0712f8f8b8b8fa0ef@...kaller.appspotmail.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>, syzkaller-bugs <syzkaller-bugs@...glegroups.com> Subject: Re: kernel BUG at mm/page-writeback.c:LINE! On Tue, Jan 12, 2021 at 2:44 AM Jan Kara <jack@...e.cz> wrote: > > On Fri 08-01-21 18:04:21, Linus Torvalds wrote: > > > > Oh, and Michael Larabel (of phoronix) reports that that one-liner does > > something bad to a few PostgreSQL tests, on the order of 5-10% > > regression on some machines (but apparently not others). > > Do you have more details? From my experience (we do regular pgbench runs > for various kernels in various configs in SUSE) PostgreSQL numbers tend to > be somewhat noisy and more dependent on CPU scheduling and NUMA locality > than anything else. But it very much depends on the exact config passed to > pgbench so that's why I'm asking... No, I don't really have many more details. I don't have things like raw numbers or exact configurations, but Michael has been very responsive if you ask, so if you are interested, just email him at Michael Larabel <Michael@...haellarabel.com>. It wasn't NUMA - apparently the machines he saw this on were just plain consumer setups, and his larger machines didn't actually show the effect. But yes, I suspect it was some scheduling artifact, and probably just fairly random noise from just changing the scheduling pattern a bit. Linus
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