Re: invalidate cache

On Fri, 2008-04-04 at 13:46 +0200, Jens Axboe wrote:
> On Wed, Apr 02 2008, Zhang, Yanmin wrote:
> > Jens,
> >
> > I have a sync read testing with fio. Parameter loops=3 means
> > repeating the read for 3 times. I want to invalidate the page cache
> > before the testing, but keep cache among the loops.
> >
> > If the files already exist before testing, I could drop cache by
> > /proc/sys/vm/drop_caches. But if the files don't exist, fio will create
> > them. So if I set invalidate=0, the cache will be kept before the real testing.
> >
> > Is it possible to drop file cache in function extend_file if the file is
> > extended? I mean, just drop the extended length?
>
> I think it's a good idea to drop the extended length by default, that
> way the cache state is identical to next time that job is run. I've
> committed such a change, diff is below.
Thanks a lot! I think the patch also fixes another issue that direct-I/O testing
doesn't invalidate page cache.

-yanmin

>
> diff --git a/filesetup.c b/filesetup.c
> index e847276..98479fd 100644
> --- a/filesetup.c
> +++ b/filesetup.c
> @@ -13,6 +13,9 @@
>
> static int root_warn;
>
> +/*
> + * Leaves f->fd open on success, caller must close
> + */
> static int extend_file(struct thread_data *td, struct fio_file *f)
> {
> int r, new_layout = 0, unlink_file = 0, flags;
> @@ -105,8 +108,6 @@ static int extend_file(struct thread_data *td, struct fio_file *f)
>
> free(b);
> done:
> - close(f->fd);
> - f->fd = -1;
> return 0;
> err:
> close(f->fd);
> @@ -182,23 +183,27 @@ static int get_file_size(struct thread_data *td, struct fio_file *f)
> return 0;
> }
>
> -int file_invalidate_cache(struct thread_data *td, struct fio_file *f)
> +static int __file_invalidate_cache(struct thread_data *td, struct fio_file *f,
> + unsigned long long off,
> + unsigned long long len)
> {
> int ret = 0;
>
> - dprint(FD_IO, "invalidate cache (%d)\n", td->o.odirect);
> + if (len == -1ULL)
> + len = f->io_size;
> + if (off == -1ULL)
> + off = f->file_offset;
>
> - if (td->o.odirect)
> - return 0;
> + dprint(FD_IO, "invalidate cache %s: %llu/%llu\n", f->file_name, off,
> + len);
>
> /*
> * FIXME: add blockdev flushing too
> */
> if (f->mmap)
> - ret = madvise(f->mmap, f->io_size, MADV_DONTNEED);
> + ret = madvise(f->mmap, len, MADV_DONTNEED);
> else if (f->filetype == FIO_TYPE_FILE) {
> - ret = fadvise(f->fd, f->file_offset, f->io_size,
> - POSIX_FADV_DONTNEED);
> + ret = fadvise(f->fd, off, len, POSIX_FADV_DONTNEED);
> } else if (f->filetype == FIO_TYPE_BD) {
> ret = blockdev_invalidate_cache(f->fd);
> if (ret < 0 && errno == EACCES && geteuid()) {
> @@ -215,9 +220,18 @@ int file_invalidate_cache(struct thread_data *td, struct fio_file *f)
> if (ret < 0) {
> td_verror(td, errno, "invalidate_cache");
> return 1;
> + } else if (ret > 0) {
> + td_verror(td, ret, "invalidate_cache");
> + return 1;
> }
>
> return ret;
> +
> +}
> +
> +int file_invalidate_cache(struct thread_data *td, struct fio_file *f)
> +{
> + return __file_invalidate_cache(td, f, -1, -1);
> }
>
> int generic_close_file(struct thread_data fio_unused *td, struct fio_file *f)
> @@ -526,15 +540,26 @@ int setup_files(struct thread_data *td)
> td->o.name, need_extend, extend_size >> 20);
>
> for_each_file(td, f, i) {
> + unsigned long long old_len, extend_len;
> +
> if (!(f->flags & FIO_FILE_EXTEND))
> continue;
>
> assert(f->filetype == FIO_TYPE_FILE);
> f->flags &= ~FIO_FILE_EXTEND;
> + old_len = f->real_file_size;
> + extend_len = f->io_size + f->file_offset - old_len;
> f->real_file_size = (f->io_size + f->file_offset);
> err = extend_file(td, f);
> if (err)
> break;
> +
> + err = __file_invalidate_cache(td, f, old_len,
> + extend_len);
> + close(f->fd);
> + f->fd = -1;
> + if (err)
> + break;
> }
> temp_stall_ts = 0;
> }
>
Received on Mon Apr 07 2008 - 03:37:06 CEST