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9p: optimize p9_fcall struct

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p9_fcall has a 1 byte hole followed by more data and then a single byte
element:

struct p9_fcall {
	u32                        size;                 /*     0     4 */
	u8                         id;                   /*     4     1 */

	/* XXX 1 byte hole, try to pack */

	u16                        tag;                  /*     6     2 */
	size_t                     offset;               /*     8     8 */
	size_t                     capacity;             /*    16     8 */
	struct kmem_cache *        cache;                /*    24     8 */
	u8 *                       sdata;                /*    32     8 */
	bool                       zc;                   /*    40     1 */

	/* size: 48, cachelines: 1, members: 8 */
	/* sum members: 40, holes: 1, sum holes: 1 */
	/* padding: 7 */
	/* last cacheline: 48 bytes */
};

move `zc` up to optimize it:

struct p9_fcall {
	u32                        size;                 /*     0     4 */
	u8                         id;                   /*     4     1 */
	bool                       zc;                   /*     5     1 */
	u16                        tag;                  /*     6     2 */
	size_t                     offset;               /*     8     8 */
	size_t                     capacity;             /*    16     8 */
	struct kmem_cache *        cache;                /*    24     8 */
	u8 *                       sdata;                /*    32     8 */

	/* size: 40, cachelines: 1, members: 8 */
	/* last cacheline: 40 bytes */
};

This in turn also makes p9_req_t 16 bytes smaller (152 -> 136) as it
contains two of these.

Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Message-ID: <20261029060014.3-1-asmadeus@codewreck.org>
This commit is contained in:
Dominique Martinet 2026-10-29 06:00:12 +00:00
parent 241d469012
commit 35ecd40c0d
1 changed files with 1 additions and 1 deletions
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2
include/net/9p/9p.h
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@ -581,6 +581,7 @@ struct p9_rstatfs {
struct p9_fcall {
u32 size;
u8 id;
bool zc;
u16 tag;
size_t offset;
@ -588,7 +589,6 @@ struct p9_fcall {
struct kmem_cache *cache;
u8 *sdata;
bool zc;
};
int p9_errstr2errno(char *errstr, int len);