| Message ID | 20170206173306.20603-6-dgilbert@redhat.com |
|---|---|
| State | New |
| Headers | show |
"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote: > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > 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 <dgilbert@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> But ... > --- > exec.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/exec.c b/exec.c > index e040cdf..c25f6b3 100644 > --- a/exec.c > +++ b/exec.c > @@ -3324,9 +3324,20 @@ 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) > - 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); Why can't we use fallocate() when !CONFIG_MADVISE? or even ... if (rb->page_size == qemu_host_page_size) { #if defined(CONFIG_MADVISE) ret = qemu_madvise(host_startaddr, length, QEMU_MADV_DONTNEED); #endif } if (ret == -1) { /* 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 }
* Juan Quintela (quintela@redhat.com) wrote: > "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote: > > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > > > 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 <dgilbert@redhat.com> > > Reviewed-by: Juan Quintela <quintela@redhat.com> > > But ... > > > > --- > > exec.c | 13 ++++++++++++- > > 1 file changed, 12 insertions(+), 1 deletion(-) > > > > diff --git a/exec.c b/exec.c > > index e040cdf..c25f6b3 100644 > > --- a/exec.c > > +++ b/exec.c > > @@ -3324,9 +3324,20 @@ 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) > > - 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); > > > Why can't we use fallocate() when !CONFIG_MADVISE? > > or even ... > > if (rb->page_size == qemu_host_page_size) { > #if defined(CONFIG_MADVISE) > ret = qemu_madvise(host_startaddr, length, QEMU_MADV_DONTNEED); > #endif > } > > if (ret == -1) { > /* 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 > } The fallocate only works where we have an fd, e.g. in the hugepage case; the madvise only works where we have anonymous memory. So if we don't have madvise, we can't use fallocate for normal anonymous memory. Actually, it's much more complicated than that - I've got another patch that adds support for postcopy with memory that's backed by tmpfs with shared=true and that also uses fallocate; I'm trying to decide if it also needs the madvise. Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
On 06/02/2017 18:32, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > 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 <dgilbert@redhat.com> > --- > exec.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/exec.c b/exec.c > index e040cdf..c25f6b3 100644 > --- a/exec.c > +++ b/exec.c You should move here the "#include" from PATCH 04/16 +#ifdef CONFIG_FALLOCATE_PUNCH_HOLE +#include <fcntl.h> +#include <linux/falloc.h> +#endif > @@ -3324,9 +3324,20 @@ 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) > - 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) { > ret = -errno; > error_report("ram_block_discard_range: Failed to discard range " > Reviewed-by: Laurent Vivier <lvivier@redhat.com>
diff --git a/exec.c b/exec.c index e040cdf..c25f6b3 100644 --- a/exec.c +++ b/exec.c @@ -3324,9 +3324,20 @@ 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) - 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) { ret = -errno; error_report("ram_block_discard_range: Failed to discard range "