From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41606) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ew51O-0002os-T5 for qemu-devel@nongnu.org; Wed, 14 Mar 2018 07:56:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ew51K-0004Vu-1c for qemu-devel@nongnu.org; Wed, 14 Mar 2018 07:56:42 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:40888 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ew51J-0004VW-RK for qemu-devel@nongnu.org; Wed, 14 Mar 2018 07:56:37 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1FC6C8182D1E for ; Wed, 14 Mar 2018 11:56:35 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" Date: Wed, 14 Mar 2018 11:55:50 +0000 Message-Id: <20180314115618.28831-2-dgilbert@redhat.com> In-Reply-To: <20180314115618.28831-1-dgilbert@redhat.com> References: <20180314115618.28831-1-dgilbert@redhat.com> Subject: [Qemu-devel] [PATCH v6 01/29] migrate: Update ram_block_discard_range for shared List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, mst@redhat.com, maxime.coquelin@redhat.com, marcandre.lureau@redhat.com, peterx@redhat.com, quintela@redhat.com Cc: aarcange@redhat.com From: "Dr. David Alan Gilbert" The choice of call to discard a block is getting more complicated for other cases. We use fallocate PUNCH_HOLE in any file cases; it works for both hugepage and for tmpfs. We use the DONTNEED for non-hugepage cases either where they're anonymous or where they're private. Care should be taken when trying other backing files. Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Peter Xu --- exec.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++-------------- trace-events | 3 ++- 2 files changed, 48 insertions(+), 15 deletions(-) diff --git a/exec.c b/exec.c index a9181e6417..34fdfd966e 100644 --- a/exec.c +++ b/exec.c @@ -3721,6 +3721,7 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length) } if ((start + length) <= rb->used_length) { + bool need_madvise, need_fallocate; uint8_t *host_endaddr = host_startaddr + length; if ((uintptr_t)host_endaddr & (rb->page_size - 1)) { error_report("ram_block_discard_range: Unaligned end address: %p", @@ -3730,29 +3731,60 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length) errno = ENOTSUP; /* If we are missing MADVISE etc */ - if (rb->page_size == qemu_host_page_size) { -#if defined(CONFIG_MADVISE) - /* Note: We need the madvise MADV_DONTNEED behaviour of definitely - * freeing the page. - */ - ret = madvise(host_startaddr, length, 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. + /* The logic here is messy; + * madvise DONTNEED fails for hugepages + * fallocate works on hugepages and shmem + */ + need_madvise = (rb->page_size == qemu_host_page_size); + need_fallocate = rb->fd != -1; + if (need_fallocate) { + /* For a file, this causes the area of the file to be zero'd + * if read, and for hugetlbfs also causes it to be unmapped + * so a userfault will trigger. */ #ifdef CONFIG_FALLOCATE_PUNCH_HOLE ret = fallocate(rb->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, start, length); + if (ret) { + ret = -errno; + error_report("ram_block_discard_range: Failed to fallocate " + "%s:%" PRIx64 " +%zx (%d)", + rb->idstr, start, length, ret); + goto err; + } +#else + ret = -ENOSYS; + error_report("ram_block_discard_range: fallocate not available/file" + "%s:%" PRIx64 " +%zx (%d)", + rb->idstr, start, length, ret); + goto err; #endif } - if (ret) { - ret = -errno; - error_report("ram_block_discard_range: Failed to discard range " + if (need_madvise) { + /* For normal RAM this causes it to be unmapped, + * for shared memory it causes the local mapping to disappear + * and to fall back on the file contents (which we just + * fallocate'd away). + */ +#if defined(CONFIG_MADVISE) + ret = madvise(host_startaddr, length, MADV_DONTNEED); + if (ret) { + ret = -errno; + error_report("ram_block_discard_range: Failed to discard range " + "%s:%" PRIx64 " +%zx (%d)", + rb->idstr, start, length, ret); + goto err; + } +#else + ret = -ENOSYS; + error_report("ram_block_discard_range: MADVISE not available" "%s:%" PRIx64 " +%zx (%d)", rb->idstr, start, length, ret); + goto err; +#endif } + trace_ram_block_discard_range(rb->idstr, host_startaddr, length, + need_madvise, need_fallocate, ret); } else { error_report("ram_block_discard_range: Overrun block '%s' (%" PRIu64 "/%zx/" RAM_ADDR_FMT")", diff --git a/trace-events b/trace-events index 855b0ab240..2c3e3d7690 100644 --- a/trace-events +++ b/trace-events @@ -55,9 +55,10 @@ dma_complete(void *dbs, int ret, void *cb) "dbs=%p ret=%d cb=%p" dma_blk_cb(void *dbs, int ret) "dbs=%p ret=%d" dma_map_wait(void *dbs) "dbs=%p" -# # exec.c +# exec.c find_ram_offset(uint64_t size, uint64_t offset) "size: 0x%" PRIx64 " @ 0x%" PRIx64 find_ram_offset_loop(uint64_t size, uint64_t candidate, uint64_t offset, uint64_t next, uint64_t mingap) "trying size: 0x%" PRIx64 " @ 0x%" PRIx64 ", offset: 0x%" PRIx64" next: 0x%" PRIx64 " mingap: 0x%" PRIx64 +ram_block_discard_range(const char *rbname, void *hva, size_t length, bool need_madvise, bool need_fallocate, int ret) "%s@%p + 0x%zx: madvise: %d fallocate: %d ret: %d" # memory.c memory_region_ops_read(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u" -- 2.14.3