Re: [PATCH] cifs: Add a laundromat thread for cached directories

From: ronnie sahlberg <ronniesahlberg@gmail.com>
To: Shyam Prasad N <nspmangalore@gmail.com>
Cc: Steve French <smfrench@gmail.com>,
	Ronnie Sahlberg <lsahlber@redhat.com>,
	linux-cifs <linux-cifs@vger.kernel.org>
Subject: Re: [PATCH] cifs: Add a laundromat thread for cached directories
Date: Fri, 7 Jul 2023 16:41:59 +1000	[thread overview]
Message-ID: <CAN05THTazZByLPSgrcMg8LuMhAT2=0r+znOnUkGuSdtWPVUtGw@mail.gmail.com> (raw)
In-Reply-To: <CANT5p=qxZjxpqx49BO7G-8=se2_5gEPyLOi_W-sUDm0p7VhbEQ@mail.gmail.com>

On Fri, 7 Jul 2023 at 16:37, Shyam Prasad N <nspmangalore@gmail.com> wrote:
>
> On Fri, Jul 7, 2023 at 11:20 AM ronnie sahlberg
> <ronniesahlberg@gmail.com> wrote:
> >
> > We can only cache a limited amount of entries.
> > We need to force entries to be dropped from the cache at regular
> > intervals to make room for potential new entries/different
> > directories.
> >
> > Access patterns change over time and what is the "hot" directory will
> > also change over time so we need to drop entries to make sure that
> > when some directory becomes hot there will be decent chance that it
> > will be able to become cached.
> >
> > If a directory becomes "cold" we no longer want it to take up entries
> > in our cache.
> >
>
> Makes sense.
>
> However, the value of MAX_CACHED_FIDS to 16 seems very restrictive.
> And as Steve suggested, 30s expiry seems very aggressive.
> I think we can increase both.

We can and should increase it at some stage but lets keep it small and
short for now until we feel confident it is all stable.
Once we are confident it is good we can increase these quite a bit.