linux-kernel - Re: Canvassing for network filesystem write size vs page size

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Message-ID: <1302765.1628257488@warthog.procyon.org.uk>
Date:   Fri, 06 Aug 2021 14:44:48 +0100
From:   David Howells <dhowells@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     dhowells@...hat.com, Anna Schumaker <anna.schumaker@...app.com>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Jeff Layton <jlayton@...hat.com>,
        Steve French <sfrench@...ba.org>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Mike Marshall <hubcap@...ibond.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Shyam Prasad N <nspmangalore@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-cachefs@...hat.com, linux-afs@...ts.infradead.org,
        linux-nfs@...r.kernel.org, linux-cifs@...r.kernel.org,
        ceph-devel@...r.kernel.org, v9fs-developer@...ts.sourceforge.net,
        devel@...ts.orangefs.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Canvassing for network filesystem write size vs page size

Matthew Wilcox <willy@...radead.org> wrote:

> Filesystems should not make an assumption about this ... I suspect
> the optimum page size scales with I/O bandwidth; taking PCI bandwidth
> as a reasonable proxy, it's doubled five times in twenty years.

There are a lot more factors than you make out.  Local caching, content
crypto, transport crypto, cost of setting up RPC calls, compounding calls to
multiple servers.

David