From: Jim Fehlig <firstname.lastname@example.org> To: Jan Beulich <email@example.com>, Julien Grall <firstname.lastname@example.org> Cc: Hongyan Xia <email@example.com>, Charles Arnold <CARNOLD@suse.com>, Stefano Stabellini <firstname.lastname@example.org>, Wei Liu <email@example.com>, Andrew Cooper <firstname.lastname@example.org>, Ian Jackson <email@example.com>, George Dunlap <firstname.lastname@example.org>, email@example.com Subject: Re: [Xen-devel] [PATCH] Revert "domctl: improve locking during domain destruction" Date: Thu, 26 Mar 2020 10:55:52 -0600 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <email@example.com> On 3/25/20 1:11 AM, Jan Beulich wrote: > On 24.03.2020 19:39, Julien Grall wrote: >> On 24/03/2020 16:13, Jan Beulich wrote: >>> On 24.03.2020 16:21, Hongyan Xia wrote: >>>> From: Hongyan Xia <firstname.lastname@example.org> >>>> In contrast, >>>> after dropping that commit, parallel domain destructions will just fail >>>> to take the domctl lock, creating a hypercall continuation and backing >>>> off immediately, allowing the thread that holds the lock to destroy a >>>> domain much more quickly and allowing backed-off threads to process >>>> events and irqs. >>>> >>>> On a 144-core server with 4TiB of memory, destroying 32 guests (each >>>> with 4 vcpus and 122GiB memory) simultaneously takes: >>>> >>>> before the revert: 29 minutes >>>> after the revert: 6 minutes >>> >>> This wants comparing against numbers demonstrating the bad effects of >>> the global domctl lock. Iirc they were quite a bit higher than 6 min, >>> perhaps depending on guest properties. >> >> Your original commit message doesn't contain any clue in which >> cases the domctl lock was an issue. So please provide information >> on the setups you think it will make it worse. > > I did never observe the issue myself - let's see whether one of the SUSE > people possibly involved in this back then recall (or have further > pointers; Jim, Charles?), or whether any of the (partly former) Citrix > folks do. My vague recollection is that the issue was the tool stack as > a whole stalling for far too long in particular when destroying very > large guests. I too only have a vague memory of the issue but do recall shutting down large guests (e.g. 500GB) taking a long time and blocking other toolstack operations. I haven't checked on the behavior in quite some time though. > One important aspect not discussed in the commit message > at all is that holding the domctl lock block basically _all_ tool stack > operations (including e.g. creation of new guests), whereas the new > issue attempted to be addressed is limited to just domain cleanup. I more vaguely recall shutting down the host taking a *long* time when dom0 had large amounts of memory, e.g. when it had all host memory (no dom0_mem= setting and autoballooning enabled). Regards, Jim
next prev parent reply other threads:[~2020-03-26 17:04 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-03-24 15:21 Hongyan Xia 2020-03-24 16:13 ` Jan Beulich 2020-03-24 18:39 ` Julien Grall 2020-03-25 7:11 ` Jan Beulich 2020-03-26 14:39 ` Hongyan Xia 2020-03-26 16:55 ` Jim Fehlig [this message] 2020-03-31 10:31 ` Julien Grall 2020-03-24 18:40 ` [Xen-devel] " Julien Grall
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