Jeff Garzik wrote:
Mark Lord wrote:
..
static int __init mv_init(void) { + /* Ideally, a device (second parameter) would "own" these pools. + * But for maximum memory efficiency, we really need one global + * set of each, shared among all like devices. As below. + */ + mv_crqb_pool = dma_pool_create("mv_crqb_q", NULL, MV_CRQB_Q_SZ, + MV_CRQB_Q_SZ, 0); + mv_crpb_pool = dma_pool_create("mv_crpb_q", NULL, MV_CRPB_Q_SZ, + MV_CRPB_Q_SZ, 0); + mv_sg_tbl_pool = dma_pool_create("mv_sg_tbl", NULL, MV_SG_TBL_SZ, + MV_SG_TBL_SZ, 0);Sorry, I would far rather waste a tiny bit of memory than this.
.. The waste amounts to perhaps half a page, per port. The chips have either 4 or 8 ports. But whatever. I think libata should actually provide the pools anyway, since most drivers need hardware aligned DMA memory of very similar requirements. The pre-existing scheme in the driver is insufficient, as it does not guarantee correct alignment. Right now it does appear to work by accident, but there's no alignment guarantee in the interface unless pools are used. When we allocate 32 SG tables *per port*, this becomes much more of a bother, so pools are needed there to avoid waste. Having the pools per-port rather than per-chip multiplies any waste by factors of 4 or 8. I prefer not wasting memory, myself. Cheers - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
