From: Vladislav Bolkhovitin <vst@xxxxxxxx> 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. - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
