| Message ID | 20190826114834.14789-3-jthumshirn@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: support xxhash64 checksums | expand |
On Mon, Aug 26, 2019 at 01:48:32PM +0200, Johannes Thumshirn wrote: > Create a structure to encode the type and length for the known on-disk > checksums. > > This makes it easier to add new checksums later. > > Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de> > > --- > Changes to v2: > - Really remove initializer macro *doh* > > Changes to v1: > - Remove initializer macro (David) > --- > fs/btrfs/ctree.h | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h > index b161224b5a0b..139354d02dfa 100644 > --- a/fs/btrfs/ctree.h > +++ b/fs/btrfs/ctree.h > @@ -82,9 +82,12 @@ struct btrfs_ref; > */ > #define BTRFS_LINK_MAX 65535U > > -/* four bytes for CRC32 */ > -static const int btrfs_csum_sizes[] = { 4 }; > -static const char *btrfs_csum_names[] = { "crc32c" }; > +static const struct btrfs_csums { > + u16 size; > + const char *name; > +} btrfs_csums[] = { > + [BTRFS_CSUM_TYPE_CRC32] = { .size = 4, .name = "crc32c" }, > +}; In one of the previous iterations, I pointed out that the definition is in a header, thus each file that includes "ctree.h" (many of them) has a private copy of the table. With just crc32c it's just a few bytes that gets lost in the noise but now the table is going to be larger the impact will be noticeable.
On Wed, Aug 28, 2019 at 09:19:52PM +0200, David Sterba wrote: > On Mon, Aug 26, 2019 at 01:48:32PM +0200, Johannes Thumshirn wrote: > > Create a structure to encode the type and length for the known on-disk > > checksums. > > > > This makes it easier to add new checksums later. > > > > Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de> > > > > --- > > Changes to v2: > > - Really remove initializer macro *doh* > > > > Changes to v1: > > - Remove initializer macro (David) > > --- > > fs/btrfs/ctree.h | 13 ++++++++----- > > 1 file changed, 8 insertions(+), 5 deletions(-) > > > > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h > > index b161224b5a0b..139354d02dfa 100644 > > --- a/fs/btrfs/ctree.h > > +++ b/fs/btrfs/ctree.h > > @@ -82,9 +82,12 @@ struct btrfs_ref; > > */ > > #define BTRFS_LINK_MAX 65535U > > > > -/* four bytes for CRC32 */ > > -static const int btrfs_csum_sizes[] = { 4 }; > > -static const char *btrfs_csum_names[] = { "crc32c" }; > > +static const struct btrfs_csums { > > + u16 size; > > + const char *name; > > +} btrfs_csums[] = { > > + [BTRFS_CSUM_TYPE_CRC32] = { .size = 4, .name = "crc32c" }, > > +}; > > In one of the previous iterations, I pointed out that the definition is > in a header, thus each file that includes "ctree.h" (many of them) > has a private copy of the table. With just crc32c it's just a few bytes > that gets lost in the noise but now the table is going to be larger the > impact will be noticeable. With definitions moved to ctree.c and only exported the two helpers that need btrfs_csumss text data bss dec hex filename 1080108 17316 14912 1112336 10f910 btrfs.ko.before 1079655 17316 14912 1111883 10f74b btrfs.ko.after The difference is 453.
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index b161224b5a0b..139354d02dfa 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -82,9 +82,12 @@ struct btrfs_ref; */ #define BTRFS_LINK_MAX 65535U -/* four bytes for CRC32 */ -static const int btrfs_csum_sizes[] = { 4 }; -static const char *btrfs_csum_names[] = { "crc32c" }; +static const struct btrfs_csums { + u16 size; + const char *name; +} btrfs_csums[] = { + [BTRFS_CSUM_TYPE_CRC32] = { .size = 4, .name = "crc32c" }, +}; #define BTRFS_EMPTY_DIR_SIZE 0 @@ -2207,13 +2210,13 @@ static inline int btrfs_super_csum_size(const struct btrfs_super_block *s) /* * csum type is validated at mount time */ - return btrfs_csum_sizes[t]; + return btrfs_csums[t].size; } static inline const char *btrfs_super_csum_name(u16 csum_type) { /* csum type is validated at mount time */ - return btrfs_csum_names[csum_type]; + return btrfs_csums[csum_type].name; } /*
Create a structure to encode the type and length for the known on-disk checksums. This makes it easier to add new checksums later. Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de> --- Changes to v2: - Really remove initializer macro *doh* Changes to v1: - Remove initializer macro (David) --- fs/btrfs/ctree.h | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)