The patchset is against Jens' sg chaining branch. Jens removed old SCSI_MAX_PHYS_SEGMENTS hack and the maximum is always 128: http://git.kernel.org/?p=linux/kernel/git/axboe/linux-2.6-block.git;a=commit;h=d6beb57f48231f5c012fb7d55b369bc0af6b0c41 I talked to James at linuxconf.eu and he likes to provide a way to reduce sgpool memory consumption because with libata everyone (including small machines) uses the mid layer. This patch reverts sg segment size ifdefs that the current mid layer has. Later we might do something better like relating SCSI_MAX_SG_SEGMENTS with other config options like CONFIG_EMBEDDED or just having SCSI_MAX_SG_SEGMENTS in menuconfig. Now we have sg chaining code in -mm. As discussed before, it would be nice to test sg chaining code in -mm with a small SCSI_MAX_SG_SEGMENTS value like 32. --- >From 4692956cdc3db1d0cfb3f26dc7aa3925f591d392 Mon Sep 17 00:00:00 2001 From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> Date: Sat, 18 Aug 2007 19:00:47 +0900 Subject: [PATCH 1/2] revert sg segment size ifdefs This reverts sg segment size ifdefs that the current code has in order to provide a way to reduce sgpool memory consumption. Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> --- drivers/scsi/scsi_lib.c | 28 ++++++++++++++++++++-------- 1 files changed, 20 insertions(+), 8 deletions(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index f05f006..2fc2380 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -34,6 +34,13 @@ #define SG_MEMPOOL_NR ARRAY_SIZE(scsi_sg_pools) #define SG_MEMPOOL_SIZE 2 +/* + * The maximum number of SG segments that we will put inside a scatterlist + * (unless chaining is used). Should ideally fit inside a single page, to + * avoid a higher order allocation. + */ +#define SCSI_MAX_SG_SEGMENTS 128 + struct scsi_host_sg_pool { size_t size; char *name; @@ -45,9 +52,15 @@ struct scsi_host_sg_pool { static struct scsi_host_sg_pool scsi_sg_pools[] = { SP(8), SP(16), +#if (SCSI_MAX_SG_SEGMENTS > 16) SP(32), +#if (SCSI_MAX_SG_SEGMENTS > 32) SP(64), +#if (SCSI_MAX_SG_SEGMENTS > 64) SP(128), +#endif +#endif +#endif }; #undef SP @@ -690,13 +703,6 @@ static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int uptodate, } /* - * The maximum number of SG segments that we will put inside a scatterlist - * (unless chaining is used). Should ideally fit inside a single page, to - * avoid a higher order allocation. - */ -#define SCSI_MAX_SG_SEGMENTS 128 - -/* * Like SCSI_MAX_SG_SEGMENTS, but for archs that have sg chaining. This limit * is totally arbitrary, a setting of 2048 will get you at least 8mb ios. */ @@ -713,15 +719,21 @@ static inline unsigned int scsi_sgtable_index(unsigned short nents) case 9 ... 16: index = 1; break; +#if (SCSI_MAX_SG_SEGMENTS > 16) case 17 ... 32: index = 2; break; +#if (SCSI_MAX_SG_SEGMENTS > 32) case 33 ... 64: index = 3; break; - case 65 ... SCSI_MAX_SG_SEGMENTS: +#if (SCSI_MAX_SG_SEGMENTS > 64) + case 65 ... 128: index = 4; break; +#endif +#endif +#endif default: printk(KERN_ERR "scsi: bad segment count=%d\n", nents); BUG(); -- 1.5.2.4 - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
