search for: backpressur

> ssh has to set NONBLOCK otherwise it can, well, block - there's > no way for ssh to know a priori how much data it can write to a fd. I don't know anything about how ssh is structured, but I think it must be a bit more complicated than that. Ssh only sets O_NONBLOCK on an fd if isatty(fd) returns false, so it's able to function with blocking input and output if the relevant

...ncreases single stream throughput. The virtio-net driver currently cleans tx descriptors on transmission of new packets in ndo_start_xmit. Latency depends on new traffic, so is unbounded. To avoid deadlock when a socket reaches its snd limit, packets are orphaned on tranmission. This breaks socket backpressure, including TSQ. Napi increases the number of interrupts generated compared to the current model, which keeps interrupts disabled as long as the ring has enough free descriptors. Keep tx napi optional for now. Follow-on patches will reduce the interrupt cost. Signed-off-by: Willem de Bruijn <w...

...ry alloc failure in the middle of receive. As Eric mentioned, we can drop the packet and free the remaining (num_buf) frags. Michael, perhaps I'm missing something, but why would you prefer pre-allocating buffers in this case? If the guest kernel is OOM'ing, dropping packets should provide backpressure. Also, we could just as easily fail the initial skb alloc in page_to_skb, and I think that case also needs to be handled now in the same fashion as a memory allocation failure in receive_mergeable. Best, Mike

On Tue, Nov 19, 2013 at 06:03:48AM -0800, Eric Dumazet wrote: > On Tue, 2013-11-19 at 16:05 +0800, Jason Wang wrote: > > We need to drop the refcnt of page when we fail to allocate an skb for frag > > list, otherwise it will be leaked. The bug was introduced by commit > > 2613af0ed18a11d5c566a81f9a6510b73180660a ("virtio_net: migrate mergeable rx > > buffers to page

On Tue, Nov 19, 2013 at 06:03:48AM -0800, Eric Dumazet wrote: > On Tue, 2013-11-19 at 16:05 +0800, Jason Wang wrote: > > We need to drop the refcnt of page when we fail to allocate an skb for frag > > list, otherwise it will be leaked. The bug was introduced by commit > > 2613af0ed18a11d5c566a81f9a6510b73180660a ("virtio_net: migrate mergeable rx > > buffers to page

...hroughput. > > The virtio-net driver currently cleans tx descriptors on transmission > of new packets in ndo_start_xmit. Latency depends on new traffic, so > is unbounded. To avoid deadlock when a socket reaches its snd limit, > packets are orphaned on tranmission. This breaks socket backpressure, > including TSQ. > > Napi increases the number of interrupts generated compared to the > current model, which keeps interrupts disabled as long as the ring > has enough free descriptors. Keep tx napi optional and disabled for > now. Follow-on patches will reduce the interrupt co...

...roughput. > > The virtio-net driver currently cleans tx descriptors on transmission > of new packets in ndo_start_xmit. Latency depends on new traffic, so > is unbounded. To avoid deadlock when a socket reaches its snd limit, > packets are orphaned on tranmission. This breaks socket backpressure, > including TSQ. > > Napi increases the number of interrupts generated compared to the > current model, which keeps interrupts disabled as long as the ring > has enough free descriptors. Keep tx napi optional for now. Follow-on > patches will reduce the interrupt cost. > &g...

...ncreases single stream throughput. The virtio-net driver currently cleans tx descriptors on transmission of new packets in ndo_start_xmit. Latency depends on new traffic, so is unbounded. To avoid deadlock when a socket reaches its snd limit, packets are orphaned on tranmission. This breaks socket backpressure, including TSQ. Napi increases the number of interrupts generated compared to the current model, which keeps interrupts disabled as long as the ring has enough free descriptors. Keep tx napi optional and disabled for now. Follow-on patches will reduce the interrupt cost. Signed-off-by: Willem de...

From: Willem de Bruijn <willemb at google.com> Add napi for virtio-net transmit completion processing. Based on previous patchsets by Jason Wang: [RFC V7 PATCH 0/7] enable tx interrupts for virtio-net http://lkml.iu.edu/hypermail/linux/kernel/1505.3/00245.html Changes: RFC -> v1: - dropped vhost interrupt moderation patch: not needed and likely expensive at light

From: Willem de Bruijn <willemb at google.com> Add napi for virtio-net transmit completion processing. Based on previous patchsets by Jason Wang: [RFC V7 PATCH 0/7] enable tx interrupts for virtio-net http://lkml.iu.edu/hypermail/linux/kernel/1505.3/00245.html Changes: RFC -> v1: - dropped vhost interrupt moderation patch: not needed and likely expensive at light

...ncreases single stream throughput. The virtio-net driver currently cleans tx descriptors on transmission of new packets in ndo_start_xmit. Latency depends on new traffic, so is unbounded. To avoid deadlock when a socket reaches its snd limit, packets are orphaned on tranmission. This breaks socket backpressure, including TSQ. Napi increases the number of interrupts generated compared to the current model, which keeps interrupts disabled as long as the ring has enough free descriptors. Keep tx napi optional and disabled for now. Follow-on patches will reduce the interrupt cost. Signed-off-by: Willem de...

Would it be worthwhile to implement heuristics to auto-tune ''recordsize'', or would that not be worth the effort? -- Regards, Jeremy

From: Willem de Bruijn <willemb at google.com> Add napi for virtio-net transmit completion processing. Changes: v1 -> v2: - disable by default - disable unless affinity_hint_set because cache misses add up to a third higher cycle cost, e.g., in TCP_RR tests. This is not limited to the patch that enables tx completion cleaning in rx napi. - use trylock to

From: Willem de Bruijn <willemb at google.com> Add napi for virtio-net transmit completion processing. Changes: v1 -> v2: - disable by default - disable unless affinity_hint_set because cache misses add up to a third higher cycle cost, e.g., in TCP_RR tests. This is not limited to the patch that enables tx completion cleaning in rx napi. - use trylock to

We run our IMAP spool on ZFS that''s derived from LUNs on a Netapp filer. There''s a great deal of churn in e-mail folders, with messages appearing and being deleted frequently. I know that ZFS uses copy-on- write, so that blocks in use are never overwritten, and that deleted blocks are added to a free list. This behavior would spread the free list all over the zpool. As well,

Hello Han, I am pleased you approve of the design and implementation of the XI shadow mechanism. And I appreciate the time and care you''ve taken in reviewing this substantial body of new code. You asked about performance statistics. With the current XI patch, we are seeing the following: - page faults times for XI are about 4 times faster than non-XI: 10.56 (non-XI) vs 2.43

From: Willem de Bruijn <willemb at google.com> Add napi for virtio-net transmit completion processing. Changes: v2 -> v3: - convert __netif_tx_trylock to __netif_tx_lock on tx napi poll ensure that the handler always cleans, to avoid deadlock - unconditionally clean in start_xmit avoid adding an unnecessary "if (use_napi)" branch - remove

From: Willem de Bruijn <willemb at google.com> Add napi for virtio-net transmit completion processing. Changes: v2 -> v3: - convert __netif_tx_trylock to __netif_tx_lock on tx napi poll ensure that the handler always cleans, to avoid deadlock - unconditionally clean in start_xmit avoid adding an unnecessary "if (use_napi)" branch - remove

ZFS works really stable on FreeBSD, but I''m biggest problem is how to control ZFS memory usage. I''ve no idea how to leash that beast. FreeBSD has a backpresure mechanism. I can register my function so it will be called when there are memory problems, which I do. I using it for ARC layer. Even with this in place under heavy load the kernel panics, because memory with KM_SLEEP