Buffered Logging?

[Ramki Ramakrishna]

I'll go ahead and open a JBS ticket to keep the ball rolling on this one,
and so we have a place to hang some patches and discussions off of. Scream
if I shouldn't.

-- ramki

On Mon, Aug 12, 2019 at 6:19 PM Ramki Ramakrishna <rramakrishna at twitter.com>
wrote:

>
> (Resent... Apologies to anyone who might see duplicates. There was an
> issue with my membership in the list which, I am guessing, has now been
> resolved.)
>
> ---------- Forwarded message ----------
> From: Ramki Ramakrishna <rramakrishna at twitter.com>
> To: hotspot-dev at openjdk.java.net
> Cc: "Liu, Xin" <xxinliu at amazon.com>, "Mathiske, Bernd" <
> mathiske at amazon.com>, "Hohensee, Paul" <hohensee at amazon.com>, John Coomes
> <jcoomes at twitter.com>, Tony Printezis <tprintezis at twitter.com>
> Bcc:
> Date: Mon, 12 Aug 2019 15:48:17 -0700
> Subject: Buffered Logging?
>
> In the JDK 7 time-frame, some folks noticed much longer than expected
> pauses that seemed to coincide with GC logging in the midst of a GC
> safepoint. In that setup, the GC logs were going to a disk file (these were
> often useful for post-mortem analyses) rather than to a RAM-based tmpfs
> which had been the original design center assumption. The vicissitudes of
> the dirty page flushing policy in Linux when
> IO load on the machine (not necessarily the JVM process doing the logging)
> could affect the length and duration of these inline logging stalls.
>
> A buffered logging scheme was then implemented by us (and independently by
> others) which we have used successfully to date to avoid these pauses in
> high i/o
> multi-tenant environments.
>
> We have recently ported the OpenJDK 8u based scheme past the Unified
> Logging related changes and have been using it on OpenJDK 11u.
>
> In various fora, some of us have heard people express an interest in such
> an implementation.
>
> Would there be appetite for this in openjdk (there are some differences
> between our scheme in OpenJDK 8u and their subsequent post-Unified-Logging
> port to OpenJDK 11)?
>
> If so, we'd like to open a JBS ticket, attach some patches rebased to
> current OpenJDK tip, and start preparing a webrev for discussion with a
> view to possible upstreaming if it converges past review/discussion/debate.
>
> PS: In recent discussion at the JVMLS, mention was made of something that
> might be similar in support of JFR streaming, so our rebase to tip and
> familiarization with any JFR-associated buffered logging might well make
> this easier or, possibly, moot.
>
> Thoughts, questions, comments, feedback?
> -- ramki
>
> --
> JVM Team, Platform Engineering, Twitter (San Francisco)
>


-- 
JVM Team, Infrastructure Engineering, Twitter (San Francisco)