* Alexander Duyck <alexander.du...@gmail.com>: > On 10/23/2015 03:17 PM, Helge Deller wrote: > >On 24.10.2015 00:00, Alexander Duyck wrote: > >>On 10/23/2015 02:08 PM, Helge Deller wrote: > >>>* Eric Dumazet <eric.duma...@gmail.com>: > >>>>On Fri, 2015-10-23 at 21:25 +0200, Helge Deller wrote: > >>>> > >>>>>Then, how about simply changing it to twice of L1_CACHE_BYTES ? > >>>>> > >>>>>#define XPS_MIN_MAP_ALLOC ((L1_CACHE_BYTES * 2 - sizeof(struct xps_map)) > >>>>>/ sizeof(u16)) > >>>> > >>>> > >>>>Seems good to me. > >>> > >>>Great! > >>> > >>>Can you then maybe give me an Acked-by or signed-off for the patch below? > >>>It further adds a compile-time check to avoid that XPS_MIN_MAP_ALLOC > >>>gets calculated to zero on any architecture - otherwise no queues would > >>>be allocated. > >>> > >>>In addition I would like to push it for v4.3 then through my parisc-tree > >>>(after keeping it in for-next for 1-2 days), together with the patch > >>>which reduces L1_CACHE_BYTES to 16 on parisc. > >>>Would that be OK too? > >>> > >>>Thanks! > >>>Helge > >>> > >>> > >>>[PATCH] net/xps: Increase initial number of xps queues > >>> > >>>Increase the number of initial allocated xps queues, so that the initial > >>>record > >>>allocates twice the size of L1_CACHE_BYTES bytes. > >>> > >>>This change is needed to copy with architectures where L1_CACHE_BYTES is > >>>defined to equal or less than 16 bytes. > >>> > >>>Signed-off-by: Helge Deller <del...@gmx.de> > >>> > >>>diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h > >>>index 2d15e38..d152788 100644 > >>>--- a/include/linux/netdevice.h > >>>+++ b/include/linux/netdevice.h > >>>@@ -718,7 +718,7 @@ struct xps_map { > >>> u16 queues[0]; > >>> }; > >>> #define XPS_MAP_SIZE(_num) (sizeof(struct xps_map) + ((_num) * > >>> sizeof(u16))) > >>>-#define XPS_MIN_MAP_ALLOC ((L1_CACHE_BYTES - sizeof(struct xps_map)) \ > >>>+#define XPS_MIN_MAP_ALLOC ((L1_CACHE_BYTES * 2 - sizeof(struct xps_map)) \ > >>> / sizeof(u16)) > >>> > >>> /* > >>>diff --git a/net/core/dev.c b/net/core/dev.c > >>>index 6bb6470..f6d6dd1 100644 > >>>--- a/net/core/dev.c > >>>+++ b/net/core/dev.c > >>>@@ -1972,6 +1972,8 @@ static struct xps_map *expand_xps_map(struct xps_map > >>>*map, > >>> int alloc_len = XPS_MIN_MAP_ALLOC; > >>> int i, pos; > >>> > >>>+ BUILD_BUG_ON(XPS_MIN_MAP_ALLOC == 0); > >>>+ > >>> for (pos = 0; map && pos < map->len; pos++) { > >>> if (map->queues[pos] != index) > >>> continue; > >>> > >>> > >> > >>Rather then leaving a potential bug you could probably rewrite the macro so > >>that it will give you at least 1. > >> > >>All you need to do is something like the following > >>#define XPS_MIN_MAP_ALLOC \ > >> ((L1_CACHE_ALIGN(offsetof(struct xps_map, queue[1])) - \ > >> sizeof(struct xps_map)) / sizeof(u16)) > >> > >>That should give you at least an XPS_MIN_MAP_ALLOC of 1. > > > >Yes, good idea! > > > >What makes me wonder though (because I have no idea about the XPS > >code/layer): > >How likely is it, that more than 1 (e.g. minimum "X") queues are needed? > >E.g. if a typical system needs at least 3 queues, then doesn't it make sense > >to allocate > >at least 3 initially by using queue[3] in your proposed patch above ? > >What would "X" be then? > > The question I would have is in how many cases it it likely that somebody > would enable this feature and point a given CPU at more than one queue. I > know the Intel drivers that make use of XPS tend to do a 1:1 mapping for > their ATR feature. I would think if anything most CPUs would probably be > mapped many:1, but you probably won't have all that many cases where it is > 1:many or many:many. > > I'd say starting with at least 1 should be fine. Worst case scenario is we > have to make a couple more calls to expand_xps_map which will likely occur > as a slow path and infrequent event anyway.
Ok, can I get then the signed-off or acked-by from you for this patch? Thanks, Helge [PATCH] net/xps: Fix calculation of initial number of xps queues The existing code breaks on architectures where the L1 cache size (L1_CACHE_BYTES) is smaller or equal the size of struct xps_map. The new code ensures that we get at minimum one initial xps queue, or even more as long as it fits into the next multiple of L1_CACHE_SIZE. Signed-off-by: Helge Deller <del...@gmx.de> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 2d15e38..2212c82 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -718,8 +718,8 @@ struct xps_map { u16 queues[0]; }; #define XPS_MAP_SIZE(_num) (sizeof(struct xps_map) + ((_num) * sizeof(u16))) -#define XPS_MIN_MAP_ALLOC ((L1_CACHE_BYTES - sizeof(struct xps_map)) \ - / sizeof(u16)) +#define XPS_MIN_MAP_ALLOC ((L1_CACHE_ALIGN(offsetof(struct xps_map, queues[1])) \ + - sizeof(struct xps_map)) / sizeof(u16)) /* * This structure holds all XPS maps for device. Maps are indexed by CPU. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html