From: boris.ostrovsky@oracle.com
To: Anchal Agarwal <anchalag@amazon.com>,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, x86@kernel.org, jgross@suse.com,
linux-pm@vger.kernel.org, linux-mm@kvack.org, kamatam@amazon.com,
sstabellini@kernel.org, konrad.wilk@oracle.com,
roger.pau@citrix.com, axboe@kernel.dk, davem@davemloft.net,
rjw@rjwysocki.net, len.brown@intel.com, pavel@ucw.cz,
peterz@infradead.org, eduval@amazon.com, sblbir@amazon.com,
xen-devel@lists.xenproject.org, vkuznets@redhat.com,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
dwmw@amazon.co.uk, benh@kernel.crashing.org
Subject: Re: [PATCH v3 10/11] xen: Update sched clock offset to avoid system instability in hibernation
Date: Sun, 13 Sep 2020 13:52:10 -0400 [thread overview]
Message-ID: <09bb5d50-ee13-133e-d5da-a342052e4271@oracle.com> (raw)
In-Reply-To: <238e837b8d4e17925801c4e85de17bdfca4ddd00.1598042152.git.anchalag@amazon.com>
On 8/21/20 6:30 PM, Anchal Agarwal wrote:
> Save/restore xen_sched_clock_offset in syscore suspend/resume during PM
> hibernation. Commit '867cefb4cb1012: ("xen: Fix x86 sched_clock() interface
> for xen")' fixes xen guest time handling during migration. A similar issue
> is seen during PM hibernation when system runs CPU intensive workload.
> Post resume pvclock resets the value to 0 however, xen sched_clock_offset
> is never updated. System instability is seen during resume from hibernation
> when system is under heavy CPU load. Since xen_sched_clock_offset is not
> updated, system does not see the monotonic clock value and the scheduler
> would then think that heavy CPU hog tasks need more time in CPU, causing
> the system to freeze
I don't think you need to explain why non-monotonic clocks are bad.
(and, in fact, the same applies to commit message in patch 8)
>
> Signed-off-by: Anchal Agarwal <anchalag@amazon.com>
> ---
> arch/x86/xen/suspend.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/xen/suspend.c b/arch/x86/xen/suspend.c
> index b12db6966af6..a62e08a11681 100644
> --- a/arch/x86/xen/suspend.c
> +++ b/arch/x86/xen/suspend.c
> @@ -98,8 +98,9 @@ static int xen_syscore_suspend(void)
> return 0;
>
> gnttab_suspend();
> -
> xen_manage_runstate_time(-1);
> + xen_save_sched_clock_offset();
> +
> xrfp.domid = DOMID_SELF;
> xrfp.gpfn = __pa(HYPERVISOR_shared_info) >> PAGE_SHIFT;
>
> @@ -120,6 +121,12 @@ static void xen_syscore_resume(void)
> xen_hvm_map_shared_info();
>
> pvclock_resume();
> +
> + /*
> + * Restore xen_sched_clock_offset during resume to maintain
> + * monotonic clock value
> + */
I'd drop this comment, we know what the call does.
-boris
> + xen_restore_sched_clock_offset();
> xen_manage_runstate_time(0);
> gnttab_resume();
> }
next prev parent reply other threads:[~2020-09-13 17:55 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 22:22 [PATCH v3 00/11] Fix PM hibernation in Xen guests Anchal Agarwal
2020-08-21 22:25 ` [PATCH v3 01/11] xen/manage: keep track of the on-going suspend mode Anchal Agarwal
2020-09-13 15:43 ` boris.ostrovsky
2020-09-14 21:47 ` Anchal Agarwal
2020-09-15 0:24 ` boris.ostrovsky
2020-09-15 18:00 ` Anchal Agarwal
2020-09-15 19:58 ` boris.ostrovsky
2020-09-21 21:54 ` Anchal Agarwal
2020-09-22 16:18 ` boris.ostrovsky
2020-09-22 23:17 ` Anchal Agarwal
[not found] ` <20200925190423.GA31885@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com>
2020-09-25 20:02 ` boris.ostrovsky
2020-09-25 22:28 ` Anchal Agarwal
2020-09-28 18:49 ` boris.ostrovsky
2020-09-30 21:29 ` Anchal Agarwal
2020-10-01 12:43 ` boris.ostrovsky
2021-05-21 5:26 ` Anchal Agarwal
2021-05-25 22:23 ` Boris Ostrovsky
2021-05-26 4:40 ` Anchal Agarwal
2021-05-26 18:29 ` Boris Ostrovsky
[not found] ` <20210528215008.GA19622@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com>
2021-06-01 14:18 ` Boris Ostrovsky
2021-06-02 19:37 ` Anchal Agarwal
2021-06-03 20:11 ` Boris Ostrovsky
2021-06-03 23:27 ` Anchal Agarwal
2021-06-04 1:49 ` Boris Ostrovsky
2020-09-13 17:07 ` boris.ostrovsky
2020-08-21 22:26 ` [PATCH v3 02/11] xenbus: add freeze/thaw/restore callbacks support Anchal Agarwal
2020-09-13 16:11 ` boris.ostrovsky
2020-09-15 19:56 ` Anchal Agarwal
2020-08-21 22:26 ` [PATCH v3 03/11] x86/xen: Introduce new function to map HYPERVISOR_shared_info on Resume Anchal Agarwal
2020-08-21 22:27 ` [PATCH v3 04/11] x86/xen: add system core suspend and resume callbacks Anchal Agarwal
2020-09-13 17:25 ` boris.ostrovsky
2020-08-21 22:27 ` [PATCH v3 05/11] genirq: Shutdown irq chips in suspend/resume during hibernation Thomas Gleixner
2020-08-22 0:36 ` Thomas Gleixner
2020-08-24 17:25 ` Anchal Agarwal
2020-08-25 13:20 ` Christoph Hellwig
2020-08-25 15:25 ` Thomas Gleixner
2020-08-21 22:28 ` [PATCH v3 06/11] xen-blkfront: add callbacks for PM suspend and hibernation Anchal Agarwal
2020-08-21 22:29 ` [PATCH v3 07/11] xen-netfront: " Anchal Agarwal
2020-08-21 22:29 ` [PATCH v3 08/11] x86/xen: save and restore steal clock during PM hibernation Anchal Agarwal
2020-08-21 22:30 ` [PATCH v3 09/11] xen: Introduce wrapper for save/restore sched clock offset Anchal Agarwal
2020-08-21 22:30 ` [PATCH v3 10/11] xen: Update sched clock offset to avoid system instability in hibernation Anchal Agarwal
2020-09-13 17:52 ` boris.ostrovsky [this message]
2020-08-21 22:31 ` [PATCH v3 11/11] PM / hibernate: update the resume offset on SNAPSHOT_SET_SWAP_AREA Anchal Agarwal
2020-08-28 18:26 ` [PATCH v3 00/11] Fix PM hibernation in Xen guests Anchal Agarwal
2020-08-28 18:29 ` Rafael J. Wysocki
2020-08-28 18:39 ` Anchal Agarwal
2020-09-11 20:44 ` Anchal Agarwal
2020-09-11 15:19 ` boris.ostrovsky
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