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SubjectRe: [Patch] ltt-relay-alloc mmap support (due to NFS lack of splice support)
* Masahiro Tamori (masahiro.tamori@gmail.com) wrote:
> Hello Mathieu,
>
> I use the following version.
> LTTV 0.12.12
> LTTng 0.110
> LTT Control 0.67
> Kernles 2.6.29-rc7
>
> The target is ARM RealviewEB.
>
> Our customer will use NFS to store trace data not storage device for
> embedded devices.
> Since newer lttng use splice() even if NFS can not support splice(),
> I create a patch to support to mmap of ltt-relay-alloc.
>
> I will send a mail to this mailing list for ltt-control patch.
> I do not know which mailing list should be posted for userland tools.
>
> Best Regards,
> Masahiro Tamori
>
>
> ltt-relay-alloc mmap support
>
> Splice syscall does not support NFS. We can not save trace data to
> NFS directory. If this feature is enabled, you can use mmap()
> instead of splice().
>


Hi Masahiro,

Maybe we should consider implementing splice() support in NFS instead ?

I removed the mmap support from the ltt-relay-alloc files because splice
is more efficient and does not require to vmap the pages. Unless there
is a strong argument telling what in NFS makes it impossible to
implement splice(), I don't really see the gain in putting back the
old mmap() mechanism we had.

Maybe the NFS people will have some information about this ?

Thanks,

Mathieu


> For embeded system, NFS must be used. Target board has not enough memory
> to save trace data and some board can not connect ATA, USB and some strage
> devices.
>
> Signed-off-by: Masahiro.Tamori@gmail.com
> ---
> ltt/Kconfig | 11 11 + 0 - 0 !
> ltt/ltt-relay-alloc.c | 88 88 + 0 - 0 !
> ltt/ltt-relay-lockless.c | 15 15 + 0 - 0 !
> 3 files changed, 114 insertions(+)
>
> Index: b/ltt/Kconfig
> ===================================================================
> --- a/ltt/Kconfig
> +++ b/ltt/Kconfig
> @@ -66,6 +66,17 @@ choice
>
> endchoice
>
> +config LTT_RELAY_ALLOC_MMAP
> + bool "Linux Trace Toolkit Relay mmap Support"
> + depends on LTT_RELAY_ALLOC
> + default y
> + help
> + Support mmap for ltt-relay.
> +
> + Splice syscall does not support NFS. We can not save trace data to
> + NFS directory. If this feature is enabled, you can use mmap()
> + instead of splice().
> +
> config LTT_SERIALIZE
> tristate "Linux Trace Toolkit Serializer"
> depends on LTT_RELAY_ALLOC
> Index: b/ltt/ltt-relay-alloc.c
> ===================================================================
> --- a/ltt/ltt-relay-alloc.c
> +++ b/ltt/ltt-relay-alloc.c
> @@ -27,6 +27,74 @@
> static DEFINE_MUTEX(relay_channels_mutex);
> static LIST_HEAD(relay_channels);
>
> +#ifdef CONFIG_LTT_RELAY_ALLOC_MMAP
> +/*
> + * close() vm_op implementation for relay file mapping.
> + */
> +static void relay_file_mmap_close(struct vm_area_struct *vma)
> +{
> +}
> +
> +/*
> + * fault() vm_op implementation for relay file mapping.
> + */
> +static int relay_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> +{
> + struct page *page = NULL;
> + struct rchan_buf *buf = vma->vm_private_data;
> + pgoff_t pgoff = vmf->pgoff;
> + struct page **pages;
> +
> + if (!buf)
> + return VM_FAULT_OOM;
> +
> + if (pgoff >= buf->page_count)
> + return VM_FAULT_SIGBUS;
> +
> + pages = buf->pages;
> + page = pages[pgoff];
> + get_page(page);
> + vmf->page = page;
> +
> + return 0;
> +}
> +
> +/*
> + * vm_ops for relay file mappings.
> + */
> +static struct vm_operations_struct relay_file_mmap_ops = {
> + .fault = relay_buf_fault,
> + .close = relay_file_mmap_close,
> +};
> +
> +/**
> + * relay_mmap_buf: - mmap channel buffer to process address space
> + * @buf: relay channel buffer
> + * @vma: vm_area_struct describing memory to be mapped
> + *
> + * Returns 0 if ok, negative on error
> + *
> + * Caller should already have grabbed mmap_sem.
> + */
> +static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
> +{
> + unsigned long length = vma->vm_end - vma->vm_start;
> +
> + if (!buf)
> + return -EBADF;
> +
> + if (length != (unsigned long)buf->chan->alloc_size)
> + return -EINVAL;
> +
> + vma->vm_ops = &relay_file_mmap_ops;
> + vma->vm_flags |= VM_DONTEXPAND;
> + vma->vm_private_data = buf;
> +
> + return 0;
> +}
> +
> +#endif /* CONFIG_LTT_RELAY_ALLOC_MMAP */
> +
> /**
> * relay_alloc_buf - allocate a channel buffer
> * @buf: the buffer struct
> @@ -601,6 +669,23 @@ static int relay_file_open(struct inode
> return nonseekable_open(inode, filp);
> }
>
> +#ifdef CONFIG_LTT_RELAY_ALLOC_MMAP
> +
> +/**
> + * relay_file_mmap - mmap file op for relay files
> + * @filp: the file
> + * @vma: the vma describing what to map
> + *
> + * Calls upon relay_mmap_buf() to map the file into user space.
> + */
> +static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
> +{
> + struct rchan_buf *buf = filp->private_data;
> + return relay_mmap_buf(buf, vma);
> +}
> +
> +#endif /* CONFIG_LTT_RELAY_ALLOC_MMAP */
> +
> /**
> * relay_file_release - release file op for relay files
> * @inode: the inode
> @@ -619,6 +704,9 @@ static int relay_file_release(struct ino
>
> const struct file_operations ltt_relay_file_operations = {
> .open = relay_file_open,
> +#ifdef CONFIG_LTT_RELAY_ALLOC_MMAP
> + .mmap = relay_file_mmap,
> +#endif
> .release = relay_file_release,
> };
> EXPORT_SYMBOL_GPL(ltt_relay_file_operations);
> Index: b/ltt/ltt-relay-lockless.c
> ===================================================================
> --- a/ltt/ltt-relay-lockless.c
> +++ b/ltt/ltt-relay-lockless.c
> @@ -427,6 +427,18 @@ static int ltt_release(struct inode *ino
> }
>
> /**
> + * ltt_mmap - mmap file op for ltt files
> + * @inode: opened inode
> + * @file: opened file
> + *
> + * Mmap implementation.
> + */
> +static int ltt_mmap(struct file *file, struct vm_area_struct *vma)
> +{
> + return ltt_relay_file_operations.mmap(file, vma);
> +}
> +
> +/**
> * ltt_poll - file op for ltt files
> * @filp: the file
> * @wait: poll table
> @@ -1590,6 +1602,9 @@ static struct ltt_transport ltt_relay_tr
> static const struct file_operations ltt_file_operations = {
> .open = ltt_open,
> .release = ltt_release,
> +#ifdef CONFIG_LTT_RELAY_ALLOC_MMAP
> + .mmap = ltt_mmap,
> +#endif
> .poll = ltt_poll,
> .splice_read = ltt_relay_file_splice_read,
> .ioctl = ltt_ioctl,

--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


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