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updated disk IO to support unbuffered files

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This commit is contained in:
Arvid Norberg
2009-01-11 02:02:34 +00:00
parent 20a0593fa3
commit 7592ad4aee
14 changed files with 785 additions and 306 deletions
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53
docs/manual.rst
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@@ -3194,6 +3194,7 @@ that will be sent to the tracker. The user-agent is a good way to identify your
int cache_size;
int cache_expiry;
bool use_read_cache;
bool disk_io_no_buffer;
std::pair<int, int> outgoing_ports;
char peer_tos;
@@ -3424,6 +3425,15 @@ in the write cache, to when it's forcefully flushed to disk. Default is 60 secon
``use_read_cache``, is set to true (default), the disk cache is also used to
cache pieces read from disk. Blocks for writing pieces takes presedence.
``disk_io_no_buffer`` defaults to true. When set to true, files are preferred
to be opened in unbuffered mode. This helps the operating system from growing
its file cache indefinitely. Currently only files whose offset in the torrent
is page aligned are opened in unbuffered mode. A page is typically 4096 bytes
and since blocks in bittorrent are 16kB, any file that is aligned to a block
or piece will get the benefit of be opened in unbuffered mode. It is therefore
recommended to make the largest file in a torrent the first file (with offset 0)
or use pad files to align all files to piece boundries.
``outgoing_ports``, if set to something other than (0, 0) is a range of ports
used to bind outgoing sockets to. This may be useful for users whose router
allows them to assign QoS classes to traffic based on its local port. It is
@@ -4949,8 +4959,8 @@ this::
struct storage_interface
{
virtual bool initialize(bool allocate_files) = 0;
virtual int read(char* buf, int slot, int offset, int size) = 0;
virtual int write(const char* buf, int slot, int offset, int size) = 0;
virtual int readv(file::iovec_t const* bufs, int slot, int offset, int num_bufs) = 0;
virtual int writev(file::iovec_t const* bufs, int slot, int offset, int num_bufs) = 0;
virtual bool move_storage(fs::path save_path) = 0;
virtual bool verify_resume_data(lazy_entry const& rd, std::string& error) = 0;
virtual bool write_resume_data(entry& rd) const = 0;
@@ -4978,31 +4988,56 @@ it will also ``ftruncate`` all files to their target size.
Returning ``true`` indicates an error occurred.
read()
readv()
------
::
int read(char* buf, int slot, int offset, int size) = 0;
int readv(file::iovec_t const* buf, int slot, int offset, int num_bufs) = 0;
This function should read the data in the given slot and at the given offset
and ``size`` number of bytes. The data is to be copied to ``buf``.
This function should read the data in the given ``slot`` and at the given ``offset``.
It should read ``num_bufs`` buffers, where the size of each buffer is specified in the
buffer array ``bufs``. The file::iovec_t type has the following members::
struct iovec_t
{
void* iov_base;
size_t iov_len;
};
The return value is the number of bytes actually read.
Every buffer in ``bufs`` can be assumed to be page aligned and be of a page aligned size,
except for the last buffer of the torrent. The buffer can be assumed to fit a fully page
aligned number of bytes though.
write()
writev()
-------
::
int write(const char* buf, int slot, int offset, int size) = 0;
This function should write the data in ``buf`` to the given slot (``slot``) at offset
``offset`` in that slot. The buffer size is ``size``.
This function should write the data to the given ``slot`` and at the given ``offset``.
It should write ``num_bufs`` buffers, where the size of each buffer is specified in the
buffer array ``bufs``. The file::iovec_t type has the following members::
struct iovec_t
{
void* iov_base;
size_t iov_len;
};
The return value is the number of bytes actually written.
Every buffer in ``bufs`` can be assumed to be page aligned and be of a page aligned size,
except for the last buffer of the torrent. The buffer can be assumed to fit a fully page
aligned number of bytes though.
This function should write the data in ``buf`` to the given slot (``slot``) at offset
``offset`` in that slot. The buffer size is ``size``.
move_storage()
--------------