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Date:      Mon, 26 Nov 2007 10:27:23 +0100
From:      gregoryd.freebsd@free.fr
To:        Robert Watson <rwatson@FreeBSD.org>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: Before & After Under The Giant Lock
Message-ID:  <1196069243.474a917b04d95@imp.free.fr>
In-Reply-To: <20071125203321.G65286@fledge.watson.org>
References:  <474830F9.90305@zirakzigil.org> <6eb82e0711240638g2cc1e54o1fb1321cafe8ff9f@mail.gmail.com> <1188.202.127.99.4.1195957922.squirrel@webmail.triplegate.net.id> <20071125110116.U63238@fledge.watson.org> <7bc80d500711251205w1a74b649mc3bd374545c1012c@mail.gmail.com> <7bc80d500711251209p3bd78bc0leb37d4cb85f677f3@mail.gmail.com> <20071125203321.G65286@fledge.watson.org>

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Hello,

Quoting Robert Watson <rwatson@FreeBSD.org>:

> No problem -- just to be clear: in 7, users can still choose between
> libpthread (m:n) and libthr (1:1), but the default is now libthr rather than
> libpthread, as libthr seemed to perform better in most if not all workloads
> of
> interest.

I thought 1:1 would perform better with I/O bound processes running several
threads.
But wouldn't a process rely on a few I/O threads for several other CPU bound
threads ? (unless specific activities such as a web server, or a database, which
would explain MySQL performing better with 1:1)

Or, to make my point (somewhat) clearer: how did you actually compare advantages
of 1:1 versus M:N when the change from the latter to the former was decided ?

And second question: would it be possible to dynamically choose one way over the
other: meaning if you know you're mostly I/O bound, then request for the 1:1
type of threads, and vice versa ?

thanks,
gregory



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