On Mon, Jun 26, 2017 at 8:35 AM, Tony Lindgren <tony@xxxxxxxxxxx> wrote: > * Will Newton <will.newton@xxxxxxxxx> [170622 03:58]: >> Reduce max_segs to 64, a value that allows allocation of an entire >> EDMA descriptor list within a single page - EDMA descriptors >> are 40 bytes and the header is much larger. This avoids doing a >> higher order GFP_ATOMIC allocation in edma_prep_slave_sg >> when setting up a transfer which can potentially fail due to >> fragmentation under heavy I/O load. >> >> The current value of 1024 is unusually high in comparison to >> other mmc host drivers which mostly use values of between 1 >> and 256. The EDMA driver at present splits lists above 20 >> segments in any case so reducing the size of lists we pass to >> it shouldn't add much overhead. > > Thanks for updating the description, makes sense to me. Sounds > like we may want to set the size different for ADMA later on if > needed and there's nothing preventing that, so: > > Acked-by: Tony Lindgren <tony@xxxxxxxxxxx> Ping? Does this one look OK? >> >> Signed-off-by: Will Newton <willn@xxxxxxxx> >> --- >> drivers/mmc/host/omap_hsmmc.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> Changes in v2: >> - More verbose commit message >> - Rebased onto current master >> >> diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c >> index 8c39dcc..bbcca93 100644 >> --- a/drivers/mmc/host/omap_hsmmc.c >> +++ b/drivers/mmc/host/omap_hsmmc.c >> @@ -2097,9 +2097,9 @@ static int omap_hsmmc_probe(struct platform_device *pdev) >> host->dbclk = NULL; >> } >> >> - /* Since we do only SG emulation, we can have as many segs >> - * as we want. */ >> - mmc->max_segs = 1024; >> + /* Set this to a value that allows allocating an entire descriptor >> + * list within a page (zero order allocation). */ >> + mmc->max_segs = 64; >> >> mmc->max_blk_size = 512; /* Block Length at max can be 1024 */ >> mmc->max_blk_count = 0xFFFF; /* No. of Blocks is 16 bits */ >> -- >> 2.9.4 >> -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
