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Date: Wed, 4 Nov 2015 21:43:15 -0500 From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> To: Bob Liu <bob.liu@...cle.com> Cc: xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org, roger.pau@...rix.com, felipe.franciosi@...rix.com, axboe@...com, avanzini.arianna@...il.com, rafal.mielniczuk@...rix.com, jonathan.davies@...rix.com, david.vrabel@...rix.com Subject: Re: [PATCH v4 10/10] xen/blkback: make pool of persistent grants and free pages per-queue On Mon, Nov 02, 2015 at 12:21:46PM +0800, Bob Liu wrote: > Make pool of persistent grants and free pages per-queue/ring instead of > per-device to get better scalability. How much better scalability do we get? .. snip .. > > > /* > - * pers_gnts_lock must be used around all the persistent grant helpers > - * because blkback may use multi-thread/queue for each backend. > + * We don't need locking around the persistent grant helpers > + * because blkback uses a single-thread for each backed, so we s/backed/backend/ > + * can be sure that this functions will never be called recursively. > + * > + * The only exception to that is put_persistent_grant, that can be called > + * from interrupt context (by xen_blkbk_unmap), so we have to use atomic > + * bit operations to modify the flags of a persistent grant and to count > + * the number of used grants. > */ ..snip.. > --- a/drivers/block/xen-blkback/common.h > +++ b/drivers/block/xen-blkback/common.h > @@ -282,6 +282,22 @@ struct xen_blkif_ring { > spinlock_t pending_free_lock; > wait_queue_head_t pending_free_wq; > > + /* buffer of free pages to map grant refs */ Full stop. > + spinlock_t free_pages_lock; > + int free_pages_num; > + struct list_head free_pages; > + > + /* tree to store persistent grants */ Full stop. > + spinlock_t pers_gnts_lock; > + struct rb_root persistent_gnts; > + unsigned int persistent_gnt_c; > + atomic_t persistent_gnt_in_use; > + unsigned long next_lru; > + > + /* used by the kworker that offload work from the persistent purge */ Full stop. > + struct list_head persistent_purge_list; > + struct work_struct persistent_purge_work; > + > /* statistics */ > unsigned long st_print; > unsigned long long st_rd_req; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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