Date: Sat, 15 Aug 1998 16:32:49 -0700 From: David Greenman <dg@root.com> To: zhihuizhang <bf20761@binghamton.edu> Cc: hackers <freebsd-hackers@FreeBSD.ORG> Subject: Re: Question on delayed write. Message-ID: <199808152332.QAA20267@implode.root.com> In-Reply-To: Your message of "Sat, 15 Aug 1998 16:03:03 EDT." <Pine.SOL.L3.93.980815154419.23861A-100000@bingsun1>
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> >The comment in vfs_clean_pages() in vfs_bio.c says we can set the pages in >a buffer clean to avoid VM intervention and I am quite confused with this. > >(1) Even if the field valid/dirty in vm_page structure are set to be zero, >the pageout process can get the current dirty/clean status directly from >the PTE and then write the whole page to disk. The code is: > > If (m->dirty == 0) vm_page_test_dirty(); > >(2) When there is a page shortage, the pages of the buffer can be >reclaimed without being written to disk (because we have declared them as >clean). If this happens before the delayed write happens, it will lose >data. (active pages can become inactive pages) > >Any help is appreciated. The pageout daemon won't touch pages that are attached to buffers. -DG David Greenman Co-founder/Principal Architect, The FreeBSD Project To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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