Ang: Re: [Stgt-devel] Re: [Iscsitarget-devel] stgt a new version of iscsi target?
fujita.tomonori at lab.ntt.co.jp
Sat Dec 10 09:46:58 CET 2005
From: Vladislav Bolkhovitin <vst at vlnb.net>
Subject: Re: Ang: Re: [Stgt-devel] Re: [Iscsitarget-devel] stgt a new version of iscsi target?
Date: Fri, 09 Dec 2005 18:28:58 +0300
> > Also is the page cache comment in reference to us using the page cache
> > for our reads and writes or I am not sure why you wrote that if you do
> > not do it right now.
> Hm, at first, the page cache already used somehow in fileio dev handler
> (though, with additional mem copy). At the second, fully utilize the
> page cache is one of two major improvements that are pending in scst,
> because it is required changing the kernel, which until some moment try
> to avoid. Although I prepared what is necessary for that.
> The idea basically is the following. When READ operation arrives, pages
> for all requested blocks are at first searched in the page cache
> (probably, in SIRQ context, because it isn't expensive operation) and if
> all pages are found, they are referenced and the result will be sent to
> the initiator. Then the pages will be dereferenced (so, no pages
> allocation will be done at all). Otherwise, the missed pages will be
> allocated and the command will be rescheduled to the thread, which will
> read them. Then, after the response is sent, the pages will remain in
> the page cache for future accesses. For WRITEs the processing is the
> similar, the pages with the data will be put in the page cache.
The Ardis iSCSI target code does the same thing.
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