On 09/24/12 20:11, Josef Bacik wrote:
> The reason we offload csumming is because it is CPU intensive, except it is
> not on modern intel CPUs. So check to see if we support hardware crc32c,
> and if we do just do the csumming in our current threads context. Otherwise
> we can farm it off. Thanks,
>
> Signed-off-by: Josef Bacik <jbacik@xxxxxxxxxxxx>
> ---
> fs/btrfs/disk-io.c | 17 +++++++++++++++++
> 1 files changed, 17 insertions(+), 0 deletions(-)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index dcaf556..830b9af 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -31,6 +31,7 @@
> #include <linux/migrate.h>
> #include <linux/ratelimit.h>
> #include <asm/unaligned.h>
> +#include <asm/cpufeature.h>
> #include "compat.h"
> #include "ctree.h"
> #include "disk-io.h"
> @@ -880,6 +881,22 @@ static int btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
> }
>
> /*
> + * Pretty sure I'm going to hell for this. If our CPU can do crc32cs in
> + * the hardware then there is no reason to do the csum stuff
> + * asynchronously, it will be faster to do it inline, so test to see if
> + * our CPU can do hardware crc32c and if it can just do the csum in our
> + * threads context.
> + */
> +#ifdef CONFIG_X86
> + if (cpu_has_xmm4_2) {
> + printk(KERN_ERR "doing it the fast way\n");
You'll probably go to hell for the printk...
> + ret = btree_csum_one_bio(bio);
> + if (ret)
> + return ret;
> + return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio, mirror_num, 0);
> + }
> +#endif
> + /*
> * kthread helpers are used to submit writes so that checksumming
> * can happen in parallel across all CPUs
> */
>
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