Messages in this thread | | | Date | Wed, 01 Feb 2006 11:41:16 +0100 | From | Jes Sorensen <> | Subject | Re: [patch] SGIIOC4 limit request size |
| |
Bartlomiej Zolnierkiewicz wrote: > On 01 Feb 2006 03:59:16 -0500, Jes Sorensen <jes@sgi.com> wrote: >>This one takes care of a problem with the SGI IOC4 driver where it >>hits DMA problems if the request grows too large. > > > Does this happen only for CONFIG_IA64_PAGE_SIZE_4KB=y > or CONFIG_IA64_PAGE_SIZE_8KB=y? > > from sgiioc4.c: > > /* Each Physical Region Descriptor Entry size is 16 bytes (2 * 64 bits) */ > /* IOC4 has only 1 IDE channel */ > #define IOC4_PRD_BYTES 16 > #define IOC4_PRD_ENTRIES (PAGE_SIZE /(4*IOC4_PRD_BYTES)) > > As limiting request size to 127 sectors punishes performance > wouldn't it be better to define IOC4_PRD_ENTRIES to 256 > if this is possible (would need 4 pages for PAGE_SIZE=4096 > and 2 for PAGE_SIZE=8192)?
This happens with the default page size which is 16KB, ie. IOC4_PRD_ENTRIES=256, the problem is not due to the request going beyond the number of PRD_ENTRIES. I haven't tried with smaller page sizes but I would assume the problem would be the same.
Even with this patch performance seems very reasonable.
Jes - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |