For review and comment. Patch adds two new module parameters to scsi_mod: max_dma_memory=, maximum DMA pool size, in MB (default=32 -> 32MB) makes the hard-coded limit for the DMA pool size be adjustable. This
Signed-off-by: Matt Domsch <[EMAIL PROTECTED]> is necessary for systems with large numbers of disks seen (i.e. ~112 LUNs on a SAN as seen by a FC controller), where the size of the scsi_malloc() pool would consume all of ZONE_DMA, leaving none for other users. This lets a system admin set a limit on how much memory to use for the scsi_malloc() pool. If set too low, fewer outstanding commands can be issued at once, so it's only a performance issue. use_zone_normal=, 1 if scsi_malloc() can safely use ZONE_NORMAL instead of ZONE_DMA By default, scsi_malloc() uses ZONE_DMA memory. On x86 and x86_64, ZONE_DMA is only 16MB, though if you've got a lot of disks, it could try to consume all of that. This lets scsi_malloc() use ZONE_NORMAL instead of ZONE_DMA, which of course is only safe if all your SCSI controllers are 64-bit-address-capable (most high-end cards today are). This flag lets you have lots more memory available to scsi_malloc() than would be available if it were forced to use only ZONE_DMA, and frees up the space it would otherwise have consumed from ZONE_DMA for other users. Tested lightly on x86_64 on EM64T systems with 8GB RAM and up to 112 LUNs visible (14x8 paths, 28x4 paths, ...) Thanks, Matt -- Matt Domsch Software Architect Dell Linux Solutions linux.dell.com & www.dell.com/linux Linux on Dell mailing lists @ http://lists.us.dell.com ===== drivers/scsi/scsi_dma.c 1.2 vs edited ===== --- 1.2/drivers/scsi/scsi_dma.c 2002-02-05 08:10:27 -06:00 +++ edited/drivers/scsi/scsi_dma.c 2005-03-18 11:31:11 -06:00 @@ -46,6 +46,29 @@ unsigned int scsi_dma_free_sectors = 0; unsigned int scsi_need_isa_buffer = 0; static unsigned char **dma_malloc_pages = NULL; +static unsigned int max_dma_memory = 32; /* 32MB */ +MODULE_PARM(max_dma_memory, "l"); +MODULE_PARM_DESC(max_dma_memory, "maximum DMA pool size, in MB (default=32 -> 32MB)"); + + +/* This flag is unsafe under these conditions: + * - you've got a <64-bit addressable SCSI controller, >4GB RAM, and an architecture where ZONE_NORMAL + * extends above 4GB (any 64-bit architecture) + * or + * - you've got an old ISA card with host->unchecked_isa_dma=1 + * + * This implies that it is really safe only with 64-bit addressable SCSI controllers + */ +static unsigned int use_zone_normal; +MODULE_PARM(use_zone_normal, "i"); +MODULE_PARM_DESC(use_zone_normal, "1 if scsi_malloc() can safely use ZONE_NORMAL instead of ZONE_DMA"); + +static inline unsigned int dma_gfp_flags() +{ + return use_zone_normal ? GFP_ATOMIC : GFP_ATOMIC | GFP_DMA; +} + + /* * Function: scsi_malloc * @@ -287,7 +310,7 @@ void scsi_resize_dma_pool(void) #endif /* limit DMA memory to 32MB: */ - new_dma_sectors = (new_dma_sectors + 15) & 0xfff0; + new_dma_sectors = min(new_dma_sectors + 15, (max_dma_memory * 1024 * 2)) & 0xfffffff0; /* * We never shrink the buffers - this leads to @@ -330,7 +353,7 @@ void scsi_resize_dma_pool(void) for (i = dma_sectors / SECTORS_PER_PAGE; i < new_dma_sectors / SECTORS_PER_PAGE; i++) { new_dma_malloc_pages[i] = (unsigned char *) - __get_free_pages(GFP_ATOMIC | GFP_DMA, 0); + __get_free_pages(dma_gfp_flags(), 0); if (!new_dma_malloc_pages[i]) break; } @@ -430,7 +453,7 @@ int scsi_init_minimal_dma_pool(void) if (dma_malloc_pages) { memset(dma_malloc_pages, 0, size); dma_malloc_pages[0] = (unsigned char *) - __get_free_pages(GFP_ATOMIC | GFP_DMA, 0); + __get_free_pages(dma_gfp_flags(), 0); if (dma_malloc_pages[0]) has_space = 1; } - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
