From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38549) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cYHTt-0002wm-Bz for qemu-devel@nongnu.org; Mon, 30 Jan 2017 14:19:14 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cYHTp-00050n-UK for qemu-devel@nongnu.org; Mon, 30 Jan 2017 14:19:13 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59408) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cYHTp-00050T-Ko for qemu-devel@nongnu.org; Mon, 30 Jan 2017 14:19:09 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B7EB3C0567B3 for ; Mon, 30 Jan 2017 19:19:09 +0000 (UTC) From: Juan Quintela In-Reply-To: <20170130184956.GG2450@work-vm> (David Alan Gilbert's message of "Mon, 30 Jan 2017 18:49:57 +0000") References: <20170106182823.1960-1-dgilbert@redhat.com> <20170106182823.1960-6-dgilbert@redhat.com> <87mvef78fq.fsf@emacs.mitica> <20170130184956.GG2450@work-vm> Reply-To: quintela@redhat.com Date: Mon, 30 Jan 2017 20:19:06 +0100 Message-ID: <871svke4ph.fsf@emacs.mitica> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH 05/15] postcopy: enhance ram_discard_range for hugepages List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: qemu-devel@nongnu.org, amit.shah@redhat.com, aarcange@redhat.com "Dr. David Alan Gilbert" wrote: > * Juan Quintela (quintela@redhat.com) wrote: >> "Dr. David Alan Gilbert (git)" wrote: >> > From: "Dr. David Alan Gilbert" >> > >> > Unfortunately madvise DONTNEED doesn't work on hugepagetlb >> > so use fallocate(FALLOC_FL_PUNCH_HOLE) >> > qemu_fd_getpagesize only sets the page based off a file >> > if the file is from hugetlbfs. >> > >> > Signed-off-by: Dr. David Alan Gilbert >> > +#if defined(CONFIG_FALLOCATE_PUNCH_HOLE) >> > +#include >> > +#endif I hate this in generic code :-() I think that the function will have to be called: qemu_ram_punch_hole(RAMBblock *, length); Put it all together at the beggining of the file? What I don't want is that if someone arrives with a way to do this in other OS, we need to put yet more ifdefs. I preffer very much that it just have to define a function with that semantics. Agreed that this is a mess, but I can't think of an easier way of doing it either :-() >> > @@ -1874,15 +1878,27 @@ int ram_discard_range(MigrationIncomingState *mis, >> > >> > if ((start + length) <= rb->used_length) { >> > uint8_t *host_endaddr = host_startaddr + length; >> > - if ((uintptr_t)host_endaddr & (qemu_host_page_size - 1)) { >> > + if ((uintptr_t)host_endaddr & (rb->page_size - 1)) { >> > error_report("ram_discard_range: Unaligned end address: %p", >> > host_endaddr); >> > goto err; >> > } >> > - errno = ENOTSUP; >> > + errno = ENOTSUP; /* If we are missing MADVISE etc */ >> > + >> > + if (rb->page_size == qemu_host_page_size) { >> > #if defined(CONFIG_MADVISE) >> > - ret = qemu_madvise(host_startaddr, length, QEMU_MADV_DONTNEED); >> > + ret = qemu_madvise(host_startaddr, length, QEMU_MADV_DONTNEED); >> > #endif >> > + } else { >> > + /* Huge page case - unfortunately it can't do DONTNEED, but >> > + * it can do the equivalent by FALLOC_FL_PUNCH_HOLE in the >> > + * huge page file. >> > + */ >> > +#ifdef CONFIG_FALLOCATE_PUNCH_HOLE >> > + ret = fallocate(rb->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, >> > + start, length); >> > +#endif >> > + } >> > if (ret) { >> > error_report("ram_discard_range: Failed to discard range " >> > "%s:%" PRIx64 " +%zx (%d)", >> >> Can we move this to qemu-posix or similar? >> qemu_punch_hole() or similar and just put all the magic there? > > I'm trying but it's tricky. > The problem is that: > a) To be able to tell which you need you need the pagesize of the > area > b) Then you need the fd if it is a hugepage > (You can get (a) from (b) by a syscall we already do once) > c) If it's normal RAM you need the memory address but... > d) If it's a hugepage you need the offset in the file > > which is a mess; so you either have to pass all those parameters, > or end up passing a RAMBlock* which doesn't feel like it should > make its way into any of the os-* files. > > I could move it to exec.c that already has some ifdef on OSs; > what do you think? > > Dave > >> For the rest, I am ok with it. > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK