From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: per-bdi-throttling: synchronous writepage doesn't work correctly From: Peter Zijlstra In-Reply-To: References: <1193935886.27652.313.camel@twins> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-dSa74V+mZJnKJ/sKvoKp" Date: Thu, 01 Nov 2007 18:09:09 +0100 Message-Id: <1193936949.27652.321.camel@twins> Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org Return-Path: To: Miklos Szeredi Cc: jdike@addtoit.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: --=-dSa74V+mZJnKJ/sKvoKp Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Thu, 2007-11-01 at 18:00 +0100, Miklos Szeredi wrote: > > > Hi, > > >=20 > > > It looks like bdi_thresh will always be zero if filesystem does > > > synchronous writepage, resulting in very poor write performance. > > >=20 > > > Hostfs (UML) is one such example, but there might be others. > > >=20 > > > The only solution I can think of is to add a set_page_writeback(); > > > end_page_writeback() pair (or some reduced variant, that only does > > > the proportions magic). But that means auditing quite a few > > > filesystems... > >=20 > > Ouch... > >=20 > > I take it there is no other function that is shared between all these > > writeout paths which we could stick a bdi_writeout_inc(bdi) in? >=20 > No, and you can't detect it from the callers either I think. The page not having PG_writeback set on return is a hint, but not fool proof, it could be the device is just blazing fast. I guess there is nothing to it but for me to grep writepage and manually look at all hits... --=-dSa74V+mZJnKJ/sKvoKp Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQBHKgg1XA2jU0ANEf4RAn80AJ47Qu81P9UszpqrtAsdBGtbBKwqUgCbBQJg 6hM3NjbF6zxEbRDKfNQgLyc= =AUR4 -----END PGP SIGNATURE----- --=-dSa74V+mZJnKJ/sKvoKp-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org